/usr/src/gnu/usr.bin/clang/libclangAST/../../../llvm/clang/lib/AST/ExprConstant.cpp

Bug Summary

File:	src/gnu/usr.bin/clang/libclangAST/../../../llvm/clang/lib/AST/ExprConstant.cpp
Warning:	line 5966, column 57 Called C++ object pointer is null
Annotated Source Code

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clang -cc1 -cc1 -triple amd64-unknown-openbsd7.0 -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name ExprConstant.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -mrelocation-model static -mframe-pointer=all -relaxed-aliasing -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/usr/src/gnu/usr.bin/clang/libclangAST/obj -resource-dir /usr/local/lib/clang/13.0.0 -I /usr/src/gnu/usr.bin/clang/libclangAST/obj/../include/clang/AST -I /usr/src/gnu/usr.bin/clang/libclangAST/../../../llvm/clang/include -I /usr/src/gnu/usr.bin/clang/libclangAST/../../../llvm/llvm/include -I /usr/src/gnu/usr.bin/clang/libclangAST/../include -I /usr/src/gnu/usr.bin/clang/libclangAST/obj -I /usr/src/gnu/usr.bin/clang/libclangAST/obj/../include -D NDEBUG -D __STDC_LIMIT_MACROS -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D LLVM_PREFIX="/usr" -internal-isystem /usr/include/c++/v1 -internal-isystem /usr/local/lib/clang/13.0.0/include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/usr/src/gnu/usr.bin/clang/libclangAST/obj -ferror-limit 19 -fvisibility-inlines-hidden -fwrapv -stack-protector 2 -fno-rtti -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-valloc -fno-builtin-free -fno-builtin-strdup -fno-builtin-strndup -analyzer-output=html -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /home/ben/Projects/vmm/scan-build/2022-01-12-194120-40624-1 -x c++ /usr/src/gnu/usr.bin/clang/libclangAST/../../../llvm/clang/lib/AST/ExprConstant.cpp
/usr/src/gnu/usr.bin/clang/libclangAST/../../../llvm/clang/lib/AST/ExprConstant.cpp

→
1//===--- ExprConstant.cpp - Expression Constant Evaluator -----------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the Expr constant evaluator.
10//
11// Constant expression evaluation produces four main results:
12//
13//  * A success/failure flag indicating whether constant folding was successful.
14//    This is the 'bool' return value used by most of the code in this file. A
15//    'false' return value indicates that constant folding has failed, and any
16//    appropriate diagnostic has already been produced.
17//
18//  * An evaluated result, valid only if constant folding has not failed.
19//
20//  * A flag indicating if evaluation encountered (unevaluated) side-effects.
21//    These arise in cases such as (sideEffect(), 0) and (sideEffect() || 1),
22//    where it is possible to determine the evaluated result regardless.
23//
24//  * A set of notes indicating why the evaluation was not a constant expression
25//    (under the C++11 / C++1y rules only, at the moment), or, if folding failed
26//    too, why the expression could not be folded.
27//
28// If we are checking for a potential constant expression, failure to constant
29// fold a potential constant sub-expression will be indicated by a 'false'
30// return value (the expression could not be folded) and no diagnostic (the
31// expression is not necessarily non-constant).
32//
33//===----------------------------------------------------------------------===//

35#include "Interp/Context.h"
36#include "Interp/Frame.h"
37#include "Interp/State.h"
38#include "clang/AST/APValue.h"
39#include "clang/AST/ASTContext.h"
40#include "clang/AST/ASTDiagnostic.h"
41#include "clang/AST/ASTLambda.h"
42#include "clang/AST/Attr.h"
43#include "clang/AST/CXXInheritance.h"
44#include "clang/AST/CharUnits.h"
45#include "clang/AST/CurrentSourceLocExprScope.h"
46#include "clang/AST/Expr.h"
47#include "clang/AST/OSLog.h"
48#include "clang/AST/OptionalDiagnostic.h"
49#include "clang/AST/RecordLayout.h"
50#include "clang/AST/StmtVisitor.h"
51#include "clang/AST/TypeLoc.h"
52#include "clang/Basic/Builtins.h"
53#include "clang/Basic/TargetInfo.h"
54#include "llvm/ADT/APFixedPoint.h"
55#include "llvm/ADT/Optional.h"
56#include "llvm/ADT/SmallBitVector.h"
57#include "llvm/Support/Debug.h"
58#include "llvm/Support/SaveAndRestore.h"
59#include "llvm/Support/raw_ostream.h"
60#include <cstring>
61#include <functional>

63#define DEBUG_TYPE"exprconstant" "exprconstant"

65using namespace clang;
66using llvm::APFixedPoint;
67using llvm::APInt;
68using llvm::APSInt;
69using llvm::APFloat;
70using llvm::FixedPointSemantics;
71using llvm::Optional;

73namespace {
struct LValue;
class CallStackFrame;
class EvalInfo;

using SourceLocExprScopeGuard =
    CurrentSourceLocExprScope::SourceLocExprScopeGuard;

static QualType getType(APValue::LValueBase B) {
  return B.getType();
}

/// Get an LValue path entry, which is known to not be an array index, as a
/// field declaration.
static const FieldDecl *getAsField(APValue::LValuePathEntry E) {
  return dyn_cast_or_null<FieldDecl>(E.getAsBaseOrMember().getPointer());
}
/// Get an LValue path entry, which is known to not be an array index, as a
/// base class declaration.
static const CXXRecordDecl *getAsBaseClass(APValue::LValuePathEntry E) {
  return dyn_cast_or_null<CXXRecordDecl>(E.getAsBaseOrMember().getPointer());
}
/// Determine whether this LValue path entry for a base class names a virtual
/// base class.
static bool isVirtualBaseClass(APValue::LValuePathEntry E) {
  return E.getAsBaseOrMember().getInt();
}

/// Given an expression, determine the type used to store the result of
/// evaluating that expression.
static QualType getStorageType(const ASTContext &Ctx, const Expr *E) {
  if (E->isPRValue())
    return E->getType();
  return Ctx.getLValueReferenceType(E->getType());
}

/// Given a CallExpr, try to get the alloc_size attribute. May return null.
static const AllocSizeAttr *getAllocSizeAttr(const CallExpr *CE) {
  if (const FunctionDecl *DirectCallee = CE->getDirectCallee())
    return DirectCallee->getAttr<AllocSizeAttr>();
  if (const Decl *IndirectCallee = CE->getCalleeDecl())
    return IndirectCallee->getAttr<AllocSizeAttr>();
  return nullptr;
}

/// Attempts to unwrap a CallExpr (with an alloc_size attribute) from an Expr.
/// This will look through a single cast.
///
/// Returns null if we couldn't unwrap a function with alloc_size.
static const CallExpr *tryUnwrapAllocSizeCall(const Expr *E) {
  if (!E->getType()->isPointerType())
    return nullptr;

  E = E->IgnoreParens();
  // If we're doing a variable assignment from e.g. malloc(N), there will
  // probably be a cast of some kind. In exotic cases, we might also see a
  // top-level ExprWithCleanups. Ignore them either way.
  if (const auto *FE = dyn_cast<FullExpr>(E))
    E = FE->getSubExpr()->IgnoreParens();

  if (const auto *Cast = dyn_cast<CastExpr>(E))
    E = Cast->getSubExpr()->IgnoreParens();

  if (const auto *CE = dyn_cast<CallExpr>(E))
    return getAllocSizeAttr(CE) ? CE : nullptr;
  return nullptr;
}

/// Determines whether or not the given Base contains a call to a function
/// with the alloc_size attribute.
static bool isBaseAnAllocSizeCall(APValue::LValueBase Base) {
  const auto *E = Base.dyn_cast<const Expr *>();
  return E && E->getType()->isPointerType() && tryUnwrapAllocSizeCall(E);
}

/// Determines whether the given kind of constant expression is only ever
/// used for name mangling. If so, it's permitted to reference things that we
/// can't generate code for (in particular, dllimported functions).
static bool isForManglingOnly(ConstantExprKind Kind) {
  switch (Kind) {
  case ConstantExprKind::Normal:
  case ConstantExprKind::ClassTemplateArgument:
  case ConstantExprKind::ImmediateInvocation:
    // Note that non-type template arguments of class type are emitted as
    // template parameter objects.
    return false;

  case ConstantExprKind::NonClassTemplateArgument:
    return true;
  }
  llvm_unreachable("unknown ConstantExprKind")__builtin_unreachable();
}

static bool isTemplateArgument(ConstantExprKind Kind) {
  switch (Kind) {
  case ConstantExprKind::Normal:
  case ConstantExprKind::ImmediateInvocation:
    return false;

  case ConstantExprKind::ClassTemplateArgument:
  case ConstantExprKind::NonClassTemplateArgument:
    return true;
  }
  llvm_unreachable("unknown ConstantExprKind")__builtin_unreachable();
}

/// The bound to claim that an array of unknown bound has.
/// The value in MostDerivedArraySize is undefined in this case. So, set it
/// to an arbitrary value that's likely to loudly break things if it's used.
static const uint64_t AssumedSizeForUnsizedArray =
    std::numeric_limits<uint64_t>::max() / 2;

/// Determines if an LValue with the given LValueBase will have an unsized
/// array in its designator.
/// Find the path length and type of the most-derived subobject in the given
/// path, and find the size of the containing array, if any.
static unsigned
findMostDerivedSubobject(ASTContext &Ctx, APValue::LValueBase Base,
                         ArrayRef<APValue::LValuePathEntry> Path,
                         uint64_t &ArraySize, QualType &Type, bool &IsArray,
                         bool &FirstEntryIsUnsizedArray) {
  // This only accepts LValueBases from APValues, and APValues don't support
  // arrays that lack size info.
  assert(!isBaseAnAllocSizeCall(Base) &&((void)0)
         "Unsized arrays shouldn't appear here")((void)0);
  unsigned MostDerivedLength = 0;
  Type = getType(Base);

  for (unsigned I = 0, N = Path.size(); I != N; ++I) {
    if (Type->isArrayType()) {
      const ArrayType *AT = Ctx.getAsArrayType(Type);
      Type = AT->getElementType();
      MostDerivedLength = I + 1;
      IsArray = true;

      if (auto *CAT = dyn_cast<ConstantArrayType>(AT)) {
        ArraySize = CAT->getSize().getZExtValue();
      } else {
        assert(I == 0 && "unexpected unsized array designator")((void)0);
        FirstEntryIsUnsizedArray = true;
        ArraySize = AssumedSizeForUnsizedArray;
      }
    } else if (Type->isAnyComplexType()) {
      const ComplexType *CT = Type->castAs<ComplexType>();
      Type = CT->getElementType();
      ArraySize = 2;
      MostDerivedLength = I + 1;
      IsArray = true;
    } else if (const FieldDecl *FD = getAsField(Path[I])) {
      Type = FD->getType();
      ArraySize = 0;
      MostDerivedLength = I + 1;
      IsArray = false;
    } else {
      // Path[I] describes a base class.
      ArraySize = 0;
      IsArray = false;
    }
  }
  return MostDerivedLength;
}

/// A path from a glvalue to a subobject of that glvalue.
struct SubobjectDesignator {
  /// True if the subobject was named in a manner not supported by C++11. Such
  /// lvalues can still be folded, but they are not core constant expressions
  /// and we cannot perform lvalue-to-rvalue conversions on them.
  unsigned Invalid : 1;

  /// Is this a pointer one past the end of an object?
  unsigned IsOnePastTheEnd : 1;

  /// Indicator of whether the first entry is an unsized array.
  unsigned FirstEntryIsAnUnsizedArray : 1;

  /// Indicator of whether the most-derived object is an array element.
  unsigned MostDerivedIsArrayElement : 1;

  /// The length of the path to the most-derived object of which this is a
  /// subobject.
  unsigned MostDerivedPathLength : 28;

  /// The size of the array of which the most-derived object is an element.
  /// This will always be 0 if the most-derived object is not an array
  /// element. 0 is not an indicator of whether or not the most-derived object
  /// is an array, however, because 0-length arrays are allowed.
  ///
  /// If the current array is an unsized array, the value of this is
  /// undefined.
  uint64_t MostDerivedArraySize;

  /// The type of the most derived object referred to by this address.
  QualType MostDerivedType;

  typedef APValue::LValuePathEntry PathEntry;

  /// The entries on the path from the glvalue to the designated subobject.
  SmallVector<PathEntry, 8> Entries;

  SubobjectDesignator() : Invalid(true) {}

  explicit SubobjectDesignator(QualType T)
      : Invalid(false), IsOnePastTheEnd(false),
        FirstEntryIsAnUnsizedArray(false), MostDerivedIsArrayElement(false),
        MostDerivedPathLength(0), MostDerivedArraySize(0),
        MostDerivedType(T) {}

  SubobjectDesignator(ASTContext &Ctx, const APValue &V)
      : Invalid(!V.isLValue() || !V.hasLValuePath()), IsOnePastTheEnd(false),
        FirstEntryIsAnUnsizedArray(false), MostDerivedIsArrayElement(false),
        MostDerivedPathLength(0), MostDerivedArraySize(0) {
    assert(V.isLValue() && "Non-LValue used to make an LValue designator?")((void)0);
    if (!Invalid) {
      IsOnePastTheEnd = V.isLValueOnePastTheEnd();
      ArrayRef<PathEntry> VEntries = V.getLValuePath();
      Entries.insert(Entries.end(), VEntries.begin(), VEntries.end());
      if (V.getLValueBase()) {
        bool IsArray = false;
        bool FirstIsUnsizedArray = false;
        MostDerivedPathLength = findMostDerivedSubobject(
            Ctx, V.getLValueBase(), V.getLValuePath(), MostDerivedArraySize,
            MostDerivedType, IsArray, FirstIsUnsizedArray);
        MostDerivedIsArrayElement = IsArray;
        FirstEntryIsAnUnsizedArray = FirstIsUnsizedArray;
      }
    }
  }

  void truncate(ASTContext &Ctx, APValue::LValueBase Base,
                unsigned NewLength) {
    if (Invalid)
      return;

    assert(Base && "cannot truncate path for null pointer")((void)0);
    assert(NewLength <= Entries.size() && "not a truncation")((void)0);

    if (NewLength == Entries.size())
      return;
    Entries.resize(NewLength);

    bool IsArray = false;
    bool FirstIsUnsizedArray = false;
    MostDerivedPathLength = findMostDerivedSubobject(
        Ctx, Base, Entries, MostDerivedArraySize, MostDerivedType, IsArray,
        FirstIsUnsizedArray);
    MostDerivedIsArrayElement = IsArray;
    FirstEntryIsAnUnsizedArray = FirstIsUnsizedArray;
  }

  void setInvalid() {
    Invalid = true;
    Entries.clear();
  }

  /// Determine whether the most derived subobject is an array without a
  /// known bound.
  bool isMostDerivedAnUnsizedArray() const {
    assert(!Invalid && "Calling this makes no sense on invalid designators")((void)0);
    return Entries.size() == 1 && FirstEntryIsAnUnsizedArray;
  }

  /// Determine what the most derived array's size is. Results in an assertion
  /// failure if the most derived array lacks a size.
  uint64_t getMostDerivedArraySize() const {
    assert(!isMostDerivedAnUnsizedArray() && "Unsized array has no size")((void)0);
    return MostDerivedArraySize;
  }

  /// Determine whether this is a one-past-the-end pointer.
  bool isOnePastTheEnd() const {
    assert(!Invalid)((void)0);
    if (IsOnePastTheEnd)
      return true;
    if (!isMostDerivedAnUnsizedArray() && MostDerivedIsArrayElement &&
        Entries[MostDerivedPathLength - 1].getAsArrayIndex() ==
            MostDerivedArraySize)
      return true;
    return false;
  }

  /// Get the range of valid index adjustments in the form
  ///   {maximum value that can be subtracted from this pointer,
  ///    maximum value that can be added to this pointer}
  std::pair<uint64_t, uint64_t> validIndexAdjustments() {
    if (Invalid || isMostDerivedAnUnsizedArray())
      return {0, 0};

    // [expr.add]p4: For the purposes of these operators, a pointer to a
    // nonarray object behaves the same as a pointer to the first element of
    // an array of length one with the type of the object as its element type.
    bool IsArray = MostDerivedPathLength == Entries.size() &&
                   MostDerivedIsArrayElement;
    uint64_t ArrayIndex = IsArray ? Entries.back().getAsArrayIndex()
                                  : (uint64_t)IsOnePastTheEnd;
    uint64_t ArraySize =
        IsArray ? getMostDerivedArraySize() : (uint64_t)1;
    return {ArrayIndex, ArraySize - ArrayIndex};
  }

  /// Check that this refers to a valid subobject.
  bool isValidSubobject() const {
    if (Invalid)
      return false;
    return !isOnePastTheEnd();
  }
  /// Check that this refers to a valid subobject, and if not, produce a
  /// relevant diagnostic and set the designator as invalid.
  bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK);

  /// Get the type of the designated object.
  QualType getType(ASTContext &Ctx) const {
    assert(!Invalid && "invalid designator has no subobject type")((void)0);
    return MostDerivedPathLength == Entries.size()
               ? MostDerivedType
               : Ctx.getRecordType(getAsBaseClass(Entries.back()));
  }

  /// Update this designator to refer to the first element within this array.
  void addArrayUnchecked(const ConstantArrayType *CAT) {
    Entries.push_back(PathEntry::ArrayIndex(0));

    // This is a most-derived object.
    MostDerivedType = CAT->getElementType();
    MostDerivedIsArrayElement = true;
    MostDerivedArraySize = CAT->getSize().getZExtValue();
    MostDerivedPathLength = Entries.size();
  }
  /// Update this designator to refer to the first element within the array of
  /// elements of type T. This is an array of unknown size.
  void addUnsizedArrayUnchecked(QualType ElemTy) {
    Entries.push_back(PathEntry::ArrayIndex(0));

    MostDerivedType = ElemTy;
    MostDerivedIsArrayElement = true;
    // The value in MostDerivedArraySize is undefined in this case. So, set it
    // to an arbitrary value that's likely to loudly break things if it's
    // used.
    MostDerivedArraySize = AssumedSizeForUnsizedArray;
    MostDerivedPathLength = Entries.size();
  }
  /// Update this designator to refer to the given base or member of this
  /// object.
  void addDeclUnchecked(const Decl *D, bool Virtual = false) {
    Entries.push_back(APValue::BaseOrMemberType(D, Virtual));

    // If this isn't a base class, it's a new most-derived object.
    if (const FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
      MostDerivedType = FD->getType();
      MostDerivedIsArrayElement = false;
      MostDerivedArraySize = 0;
      MostDerivedPathLength = Entries.size();
    }
  }
  /// Update this designator to refer to the given complex component.
  void addComplexUnchecked(QualType EltTy, bool Imag) {
    Entries.push_back(PathEntry::ArrayIndex(Imag));

    // This is technically a most-derived object, though in practice this
    // is unlikely to matter.
    MostDerivedType = EltTy;
    MostDerivedIsArrayElement = true;
    MostDerivedArraySize = 2;
    MostDerivedPathLength = Entries.size();
  }
  void diagnoseUnsizedArrayPointerArithmetic(EvalInfo &Info, const Expr *E);
  void diagnosePointerArithmetic(EvalInfo &Info, const Expr *E,
                                 const APSInt &N);
  /// Add N to the address of this subobject.
  void adjustIndex(EvalInfo &Info, const Expr *E, APSInt N) {
    if (Invalid || !N) return;
    uint64_t TruncatedN = N.extOrTrunc(64).getZExtValue();
    if (isMostDerivedAnUnsizedArray()) {
      diagnoseUnsizedArrayPointerArithmetic(Info, E);
      // Can't verify -- trust that the user is doing the right thing (or if
      // not, trust that the caller will catch the bad behavior).
      // FIXME: Should we reject if this overflows, at least?
      Entries.back() = PathEntry::ArrayIndex(
          Entries.back().getAsArrayIndex() + TruncatedN);
      return;
    }

    // [expr.add]p4: For the purposes of these operators, a pointer to a
    // nonarray object behaves the same as a pointer to the first element of
    // an array of length one with the type of the object as its element type.
    bool IsArray = MostDerivedPathLength == Entries.size() &&
                   MostDerivedIsArrayElement;
    uint64_t ArrayIndex = IsArray ? Entries.back().getAsArrayIndex()
                                  : (uint64_t)IsOnePastTheEnd;
    uint64_t ArraySize =
        IsArray ? getMostDerivedArraySize() : (uint64_t)1;

    if (N < -(int64_t)ArrayIndex || N > ArraySize - ArrayIndex) {
      // Calculate the actual index in a wide enough type, so we can include
      // it in the note.
      N = N.extend(std::max<unsigned>(N.getBitWidth() + 1, 65));
      (llvm::APInt&)N += ArrayIndex;
      assert(N.ugt(ArraySize) && "bounds check failed for in-bounds index")((void)0);
      diagnosePointerArithmetic(Info, E, N);
      setInvalid();
      return;
    }

    ArrayIndex += TruncatedN;
    assert(ArrayIndex <= ArraySize &&((void)0)
           "bounds check succeeded for out-of-bounds index")((void)0);

    if (IsArray)
      Entries.back() = PathEntry::ArrayIndex(ArrayIndex);
    else
      IsOnePastTheEnd = (ArrayIndex != 0);
  }
};

/// A scope at the end of which an object can need to be destroyed.
enum class ScopeKind {
  Block,
  FullExpression,
  Call
};

/// A reference to a particular call and its arguments.
struct CallRef {
  CallRef() : OrigCallee(), CallIndex(0), Version() {}
  CallRef(const FunctionDecl *Callee, unsigned CallIndex, unsigned Version)
      : OrigCallee(Callee), CallIndex(CallIndex), Version(Version) {}

  explicit operator bool() const { return OrigCallee; }

  /// Get the parameter that the caller initialized, corresponding to the
  /// given parameter in the callee.
  const ParmVarDecl *getOrigParam(const ParmVarDecl *PVD) const {
    return OrigCallee ? OrigCallee->getParamDecl(PVD->getFunctionScopeIndex())
                      : PVD;
  }

  /// The callee at the point where the arguments were evaluated. This might
  /// be different from the actual callee (a different redeclaration, or a
  /// virtual override), but this function's parameters are the ones that
  /// appear in the parameter map.
  const FunctionDecl *OrigCallee;
  /// The call index of the frame that holds the argument values.
  unsigned CallIndex;
  /// The version of the parameters corresponding to this call.
  unsigned Version;
};

/// A stack frame in the constexpr call stack.
class CallStackFrame : public interp::Frame {
public:
  EvalInfo &Info;

  /// Parent - The caller of this stack frame.
  CallStackFrame *Caller;

  /// Callee - The function which was called.
  const FunctionDecl *Callee;

  /// This - The binding for the this pointer in this call, if any.
  const LValue *This;

  /// Information on how to find the arguments to this call. Our arguments
  /// are stored in our parent's CallStackFrame, using the ParmVarDecl* as a
  /// key and this value as the version.
  CallRef Arguments;

  /// Source location information about the default argument or default
  /// initializer expression we're evaluating, if any.
  CurrentSourceLocExprScope CurSourceLocExprScope;

  // Note that we intentionally use std::map here so that references to
  // values are stable.
  typedef std::pair<const void *, unsigned> MapKeyTy;
  typedef std::map<MapKeyTy, APValue> MapTy;
  /// Temporaries - Temporary lvalues materialized within this stack frame.
  MapTy Temporaries;

  /// CallLoc - The location of the call expression for this call.
  SourceLocation CallLoc;

  /// Index - The call index of this call.
  unsigned Index;

  /// The stack of integers for tracking version numbers for temporaries.
  SmallVector<unsigned, 2> TempVersionStack = {1};
  unsigned CurTempVersion = TempVersionStack.back();

  unsigned getTempVersion() const { return TempVersionStack.back(); }

  void pushTempVersion() {
    TempVersionStack.push_back(++CurTempVersion);
  }

  void popTempVersion() {
    TempVersionStack.pop_back();
  }

  CallRef createCall(const FunctionDecl *Callee) {
    return {Callee, Index, ++CurTempVersion};
  }

  // FIXME: Adding this to every 'CallStackFrame' may have a nontrivial impact
  // on the overall stack usage of deeply-recursing constexpr evaluations.
  // (We should cache this map rather than recomputing it repeatedly.)
  // But let's try this and see how it goes; we can look into caching the map
  // as a later change.

  /// LambdaCaptureFields - Mapping from captured variables/this to
  /// corresponding data members in the closure class.
  llvm::DenseMap<const VarDecl *, FieldDecl *> LambdaCaptureFields;
  FieldDecl *LambdaThisCaptureField;

  CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
                 const FunctionDecl *Callee, const LValue *This,
                 CallRef Arguments);
  ~CallStackFrame();

  // Return the temporary for Key whose version number is Version.
  APValue *getTemporary(const void *Key, unsigned Version) {
    MapKeyTy KV(Key, Version);
    auto LB = Temporaries.lower_bound(KV);
    if (LB != Temporaries.end() && LB->first == KV)
60
←
Assuming the condition is true→
61
←
Taking true branch→
      return &LB->second;
62
←
Returning pointer, which participates in a condition later→
    // Pair (Key,Version) wasn't found in the map. Check that no elements
    // in the map have 'Key' as their key.
    assert((LB == Temporaries.end() || LB->first.first != Key) &&((void)0)
           (LB == Temporaries.begin() || std::prev(LB)->first.first != Key) &&((void)0)
           "Element with key 'Key' found in map")((void)0);
    return nullptr;
  }

  // Return the current temporary for Key in the map.
  APValue *getCurrentTemporary(const void *Key) {
    auto UB = Temporaries.upper_bound(MapKeyTy(Key, UINT_MAX(2147483647 *2U +1U)));
    if (UB != Temporaries.begin() && std::prev(UB)->first.first == Key)
      return &std::prev(UB)->second;
    return nullptr;
  }

  // Return the version number of the current temporary for Key.
  unsigned getCurrentTemporaryVersion(const void *Key) const {
    auto UB = Temporaries.upper_bound(MapKeyTy(Key, UINT_MAX(2147483647 *2U +1U)));
    if (UB != Temporaries.begin() && std::prev(UB)->first.first == Key)
      return std::prev(UB)->first.second;
    return 0;
  }

  /// Allocate storage for an object of type T in this stack frame.
  /// Populates LV with a handle to the created object. Key identifies
  /// the temporary within the stack frame, and must not be reused without
  /// bumping the temporary version number.
  template<typename KeyT>
  APValue &createTemporary(const KeyT *Key, QualType T,
                           ScopeKind Scope, LValue &LV);

  /// Allocate storage for a parameter of a function call made in this frame.
  APValue &createParam(CallRef Args, const ParmVarDecl *PVD, LValue &LV);

  void describe(llvm::raw_ostream &OS) override;

  Frame *getCaller() const override { return Caller; }
  SourceLocation getCallLocation() const override { return CallLoc; }
  const FunctionDecl *getCallee() const override { return Callee; }

  bool isStdFunction() const {
    for (const DeclContext *DC = Callee; DC; DC = DC->getParent())
      if (DC->isStdNamespace())
        return true;
    return false;
  }

private:
  APValue &createLocal(APValue::LValueBase Base, const void *Key, QualType T,
                       ScopeKind Scope);
};

/// Temporarily override 'this'.
class ThisOverrideRAII {
public:
  ThisOverrideRAII(CallStackFrame &Frame, const LValue *NewThis, bool Enable)
      : Frame(Frame), OldThis(Frame.This) {
    if (Enable)
      Frame.This = NewThis;
  }
  ~ThisOverrideRAII() {
    Frame.This = OldThis;
  }
private:
  CallStackFrame &Frame;
  const LValue *OldThis;
};
663}

665static bool HandleDestruction(EvalInfo &Info, const Expr *E,
                            const LValue &This, QualType ThisType);
667static bool HandleDestruction(EvalInfo &Info, SourceLocation Loc,
                            APValue::LValueBase LVBase, APValue &Value,
                            QualType T);

671namespace {
/// A cleanup, and a flag indicating whether it is lifetime-extended.
class Cleanup {
  llvm::PointerIntPair<APValue*, 2, ScopeKind> Value;
  APValue::LValueBase Base;
  QualType T;

public:
  Cleanup(APValue *Val, APValue::LValueBase Base, QualType T,
          ScopeKind Scope)
      : Value(Val, Scope), Base(Base), T(T) {}

  /// Determine whether this cleanup should be performed at the end of the
  /// given kind of scope.
  bool isDestroyedAtEndOf(ScopeKind K) const {
    return (int)Value.getInt() >= (int)K;
  }
  bool endLifetime(EvalInfo &Info, bool RunDestructors) {
    if (RunDestructors) {
      SourceLocation Loc;
      if (const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>())
        Loc = VD->getLocation();
      else if (const Expr *E = Base.dyn_cast<const Expr*>())
        Loc = E->getExprLoc();
      return HandleDestruction(Info, Loc, Base, *Value.getPointer(), T);
    }
    *Value.getPointer() = APValue();
    return true;
  }

  bool hasSideEffect() {
    return T.isDestructedType();
  }
};

/// A reference to an object whose construction we are currently evaluating.
struct ObjectUnderConstruction {
  APValue::LValueBase Base;
  ArrayRef<APValue::LValuePathEntry> Path;
  friend bool operator==(const ObjectUnderConstruction &LHS,
                         const ObjectUnderConstruction &RHS) {
    return LHS.Base == RHS.Base && LHS.Path == RHS.Path;
  }
  friend llvm::hash_code hash_value(const ObjectUnderConstruction &Obj) {
    return llvm::hash_combine(Obj.Base, Obj.Path);
  }
};
enum class ConstructionPhase {
  None,
  Bases,
  AfterBases,
  AfterFields,
  Destroying,
  DestroyingBases
};
726}

728namespace llvm {
729template<> struct DenseMapInfo<ObjectUnderConstruction> {
using Base = DenseMapInfo<APValue::LValueBase>;
static ObjectUnderConstruction getEmptyKey() {
  return {Base::getEmptyKey(), {}}; }
static ObjectUnderConstruction getTombstoneKey() {
  return {Base::getTombstoneKey(), {}};
}
static unsigned getHashValue(const ObjectUnderConstruction &Object) {
  return hash_value(Object);
}
static bool isEqual(const ObjectUnderConstruction &LHS,
                    const ObjectUnderConstruction &RHS) {
  return LHS == RHS;
}
743};
744}

746namespace {
/// A dynamically-allocated heap object.
struct DynAlloc {
  /// The value of this heap-allocated object.
  APValue Value;
  /// The allocating expression; used for diagnostics. Either a CXXNewExpr
  /// or a CallExpr (the latter is for direct calls to operator new inside
  /// std::allocator<T>::allocate).
  const Expr *AllocExpr = nullptr;

  enum Kind {
    New,
    ArrayNew,
    StdAllocator
  };

  /// Get the kind of the allocation. This must match between allocation
  /// and deallocation.
  Kind getKind() const {
    if (auto *NE = dyn_cast<CXXNewExpr>(AllocExpr))
      return NE->isArray() ? ArrayNew : New;
    assert(isa<CallExpr>(AllocExpr))((void)0);
    return StdAllocator;
  }
};

struct DynAllocOrder {
  bool operator()(DynamicAllocLValue L, DynamicAllocLValue R) const {
    return L.getIndex() < R.getIndex();
  }
};

/// EvalInfo - This is a private struct used by the evaluator to capture
/// information about a subexpression as it is folded.  It retains information
/// about the AST context, but also maintains information about the folded
/// expression.
///
/// If an expression could be evaluated, it is still possible it is not a C
/// "integer constant expression" or constant expression.  If not, this struct
/// captures information about how and why not.
///
/// One bit of information passed *into* the request for constant folding
/// indicates whether the subexpression is "evaluated" or not according to C
/// rules.  For example, the RHS of (0 && foo()) is not evaluated.  We can
/// evaluate the expression regardless of what the RHS is, but C only allows
/// certain things in certain situations.
class EvalInfo : public interp::State {
public:
  ASTContext &Ctx;

  /// EvalStatus - Contains information about the evaluation.
  Expr::EvalStatus &EvalStatus;

  /// CurrentCall - The top of the constexpr call stack.
  CallStackFrame *CurrentCall;

  /// CallStackDepth - The number of calls in the call stack right now.
  unsigned CallStackDepth;

  /// NextCallIndex - The next call index to assign.
  unsigned NextCallIndex;

  /// StepsLeft - The remaining number of evaluation steps we're permitted
  /// to perform. This is essentially a limit for the number of statements
  /// we will evaluate.
  unsigned StepsLeft;

  /// Enable the experimental new constant interpreter. If an expression is
  /// not supported by the interpreter, an error is triggered.
  bool EnableNewConstInterp;

  /// BottomFrame - The frame in which evaluation started. This must be
  /// initialized after CurrentCall and CallStackDepth.
  CallStackFrame BottomFrame;

  /// A stack of values whose lifetimes end at the end of some surrounding
  /// evaluation frame.
  llvm::SmallVector<Cleanup, 16> CleanupStack;

  /// EvaluatingDecl - This is the declaration whose initializer is being
  /// evaluated, if any.
  APValue::LValueBase EvaluatingDecl;

  enum class EvaluatingDeclKind {
    None,
    /// We're evaluating the construction of EvaluatingDecl.
    Ctor,
    /// We're evaluating the destruction of EvaluatingDecl.
    Dtor,
  };
  EvaluatingDeclKind IsEvaluatingDecl = EvaluatingDeclKind::None;

  /// EvaluatingDeclValue - This is the value being constructed for the
  /// declaration whose initializer is being evaluated, if any.
  APValue *EvaluatingDeclValue;

  /// Set of objects that are currently being constructed.
  llvm::DenseMap<ObjectUnderConstruction, ConstructionPhase>
      ObjectsUnderConstruction;

  /// Current heap allocations, along with the location where each was
  /// allocated. We use std::map here because we need stable addresses
  /// for the stored APValues.
  std::map<DynamicAllocLValue, DynAlloc, DynAllocOrder> HeapAllocs;

  /// The number of heap allocations performed so far in this evaluation.
  unsigned NumHeapAllocs = 0;

  struct EvaluatingConstructorRAII {
    EvalInfo &EI;
    ObjectUnderConstruction Object;
    bool DidInsert;
    EvaluatingConstructorRAII(EvalInfo &EI, ObjectUnderConstruction Object,
                              bool HasBases)
        : EI(EI), Object(Object) {
      DidInsert =
          EI.ObjectsUnderConstruction
              .insert({Object, HasBases ? ConstructionPhase::Bases
                                        : ConstructionPhase::AfterBases})
              .second;
    }
    void finishedConstructingBases() {
      EI.ObjectsUnderConstruction[Object] = ConstructionPhase::AfterBases;
    }
    void finishedConstructingFields() {
      EI.ObjectsUnderConstruction[Object] = ConstructionPhase::AfterFields;
    }
    ~EvaluatingConstructorRAII() {
      if (DidInsert) EI.ObjectsUnderConstruction.erase(Object);
    }
  };

  struct EvaluatingDestructorRAII {
    EvalInfo &EI;
    ObjectUnderConstruction Object;
    bool DidInsert;
    EvaluatingDestructorRAII(EvalInfo &EI, ObjectUnderConstruction Object)
        : EI(EI), Object(Object) {
      DidInsert = EI.ObjectsUnderConstruction
                      .insert({Object, ConstructionPhase::Destroying})
                      .second;
    }
    void startedDestroyingBases() {
      EI.ObjectsUnderConstruction[Object] =
          ConstructionPhase::DestroyingBases;
    }
    ~EvaluatingDestructorRAII() {
      if (DidInsert)
        EI.ObjectsUnderConstruction.erase(Object);
    }
  };

  ConstructionPhase
  isEvaluatingCtorDtor(APValue::LValueBase Base,
                       ArrayRef<APValue::LValuePathEntry> Path) {
    return ObjectsUnderConstruction.lookup({Base, Path});
  }

  /// If we're currently speculatively evaluating, the outermost call stack
  /// depth at which we can mutate state, otherwise 0.
  unsigned SpeculativeEvaluationDepth = 0;

  /// The current array initialization index, if we're performing array
  /// initialization.
  uint64_t ArrayInitIndex = -1;

  /// HasActiveDiagnostic - Was the previous diagnostic stored? If so, further
  /// notes attached to it will also be stored, otherwise they will not be.
  bool HasActiveDiagnostic;

  /// Have we emitted a diagnostic explaining why we couldn't constant
  /// fold (not just why it's not strictly a constant expression)?
  bool HasFoldFailureDiagnostic;

  /// Whether or not we're in a context where the front end requires a
  /// constant value.
  bool InConstantContext;

  /// Whether we're checking that an expression is a potential constant
  /// expression. If so, do not fail on constructs that could become constant
  /// later on (such as a use of an undefined global).
  bool CheckingPotentialConstantExpression = false;

  /// Whether we're checking for an expression that has undefined behavior.
  /// If so, we will produce warnings if we encounter an operation that is
  /// always undefined.
  ///
  /// Note that we still need to evaluate the expression normally when this
  /// is set; this is used when evaluating ICEs in C.
  bool CheckingForUndefinedBehavior = false;

  enum EvaluationMode {
    /// Evaluate as a constant expression. Stop if we find that the expression
    /// is not a constant expression.
    EM_ConstantExpression,

    /// Evaluate as a constant expression. Stop if we find that the expression
    /// is not a constant expression. Some expressions can be retried in the
    /// optimizer if we don't constant fold them here, but in an unevaluated
    /// context we try to fold them immediately since the optimizer never
    /// gets a chance to look at it.
    EM_ConstantExpressionUnevaluated,

    /// Fold the expression to a constant. Stop if we hit a side-effect that
    /// we can't model.
    EM_ConstantFold,

    /// Evaluate in any way we know how. Don't worry about side-effects that
    /// can't be modeled.
    EM_IgnoreSideEffects,
  } EvalMode;

  /// Are we checking whether the expression is a potential constant
  /// expression?
  bool checkingPotentialConstantExpression() const override  {
    return CheckingPotentialConstantExpression;
19
←
Returning the value 1, which participates in a condition later→
  }

  /// Are we checking an expression for overflow?
  // FIXME: We should check for any kind of undefined or suspicious behavior
  // in such constructs, not just overflow.
  bool checkingForUndefinedBehavior() const override {
    return CheckingForUndefinedBehavior;
  }

  EvalInfo(const ASTContext &C, Expr::EvalStatus &S, EvaluationMode Mode)
      : Ctx(const_cast<ASTContext &>(C)), EvalStatus(S), CurrentCall(nullptr),
        CallStackDepth(0), NextCallIndex(1),
        StepsLeft(C.getLangOpts().ConstexprStepLimit),
        EnableNewConstInterp(C.getLangOpts().EnableNewConstInterp),
        BottomFrame(*this, SourceLocation(), nullptr, nullptr, CallRef()),
4
←
Calling constructor for 'CallStackFrame'→
5
←
Returning from constructor for 'CallStackFrame'→
        EvaluatingDecl((const ValueDecl *)nullptr),
        EvaluatingDeclValue(nullptr), HasActiveDiagnostic(false),
        HasFoldFailureDiagnostic(false), InConstantContext(false),
        EvalMode(Mode) {}

  ~EvalInfo() {
    discardCleanups();
  }

  void setEvaluatingDecl(APValue::LValueBase Base, APValue &Value,
                         EvaluatingDeclKind EDK = EvaluatingDeclKind::Ctor) {
    EvaluatingDecl = Base;
    IsEvaluatingDecl = EDK;
    EvaluatingDeclValue = &Value;
  }

  bool CheckCallLimit(SourceLocation Loc) {
    // Don't perform any constexpr calls (other than the call we're checking)
    // when checking a potential constant expression.
    if (checkingPotentialConstantExpression() && CallStackDepth > 1)
18
←
Calling 'EvalInfo::checkingPotentialConstantExpression'→
20
←
Returning from 'EvalInfo::checkingPotentialConstantExpression'→
21
←
Assuming field 'CallStackDepth' is <= 1→
22
←
Taking false branch→
      return false;
    if (NextCallIndex == 0) {
23
←
Assuming field 'NextCallIndex' is not equal to 0→
24
←
Taking false branch→
      // NextCallIndex has wrapped around.
      FFDiag(Loc, diag::note_constexpr_call_limit_exceeded);
      return false;
    }
    if (CallStackDepth <= getLangOpts().ConstexprCallDepth)
25
←
Assuming field 'CallStackDepth' is <= field 'ConstexprCallDepth'→
26
←
Taking true branch→
      return true;
27
←
Returning the value 1, which participates in a condition later→
    FFDiag(Loc, diag::note_constexpr_depth_limit_exceeded)
      << getLangOpts().ConstexprCallDepth;
    return false;
  }

  std::pair<CallStackFrame *, unsigned>
  getCallFrameAndDepth(unsigned CallIndex) {
    assert(CallIndex && "no call index in getCallFrameAndDepth")((void)0);
    // We will eventually hit BottomFrame, which has Index 1, so Frame can't
    // be null in this loop.
    unsigned Depth = CallStackDepth;
    CallStackFrame *Frame = CurrentCall;
    while (Frame->Index > CallIndex) {
      Frame = Frame->Caller;
      --Depth;
    }
    if (Frame->Index == CallIndex)
      return {Frame, Depth};
    return {nullptr, 0};
  }

  bool nextStep(const Stmt *S) {
    if (!StepsLeft) {
      FFDiag(S->getBeginLoc(), diag::note_constexpr_step_limit_exceeded);
      return false;
    }
    --StepsLeft;
    return true;
  }

  APValue *createHeapAlloc(const Expr *E, QualType T, LValue &LV);

  Optional<DynAlloc*> lookupDynamicAlloc(DynamicAllocLValue DA) {
    Optional<DynAlloc*> Result;
    auto It = HeapAllocs.find(DA);
    if (It != HeapAllocs.end())
      Result = &It->second;
    return Result;
  }

  /// Get the allocated storage for the given parameter of the given call.
  APValue *getParamSlot(CallRef Call, const ParmVarDecl *PVD) {
    CallStackFrame *Frame = getCallFrameAndDepth(Call.CallIndex).first;
    return Frame57.1
'Frame' is non-null
1
'Frame' is non-null
1
'Frame' is non-null
1
'Frame' is non-null
1
'Frame' is non-null
1
'Frame' is non-null
 ? Frame->getTemporary(Call.getOrigParam(PVD), Call.Version)
58
←
'?' condition is true→
59
←
Calling 'CallStackFrame::getTemporary'→
63
←
Returning from 'CallStackFrame::getTemporary'→
64
←
Returning pointer, which participates in a condition later→
                 : nullptr;
  }

  /// Information about a stack frame for std::allocator<T>::[de]allocate.
  struct StdAllocatorCaller {
    unsigned FrameIndex;
    QualType ElemType;
    explicit operator bool() const { return FrameIndex != 0; };
  };

  StdAllocatorCaller getStdAllocatorCaller(StringRef FnName) const {
    for (const CallStackFrame *Call = CurrentCall; Call != &BottomFrame;
         Call = Call->Caller) {
      const auto *MD = dyn_cast_or_null<CXXMethodDecl>(Call->Callee);
      if (!MD)
        continue;
      const IdentifierInfo *FnII = MD->getIdentifier();
      if (!FnII || !FnII->isStr(FnName))
        continue;

      const auto *CTSD =
          dyn_cast<ClassTemplateSpecializationDecl>(MD->getParent());
      if (!CTSD)
        continue;

      const IdentifierInfo *ClassII = CTSD->getIdentifier();
      const TemplateArgumentList &TAL = CTSD->getTemplateArgs();
      if (CTSD->isInStdNamespace() && ClassII &&
          ClassII->isStr("allocator") && TAL.size() >= 1 &&
          TAL[0].getKind() == TemplateArgument::Type)
        return {Call->Index, TAL[0].getAsType()};
    }

    return {};
  }

  void performLifetimeExtension() {
    // Disable the cleanups for lifetime-extended temporaries.
    CleanupStack.erase(std::remove_if(CleanupStack.begin(),
                                      CleanupStack.end(),
                                      [](Cleanup &C) {
                                        return !C.isDestroyedAtEndOf(
                                            ScopeKind::FullExpression);
                                      }),
                       CleanupStack.end());
   }

  /// Throw away any remaining cleanups at the end of evaluation. If any
  /// cleanups would have had a side-effect, note that as an unmodeled
  /// side-effect and return false. Otherwise, return true.
  bool discardCleanups() {
    for (Cleanup &C : CleanupStack) {
      if (C.hasSideEffect() && !noteSideEffect()) {
        CleanupStack.clear();
        return false;
      }
    }
    CleanupStack.clear();
    return true;
  }

private:
  interp::Frame *getCurrentFrame() override { return CurrentCall; }
  const interp::Frame *getBottomFrame() const override { return &BottomFrame; }

  bool hasActiveDiagnostic() override { return HasActiveDiagnostic; }
  void setActiveDiagnostic(bool Flag) override { HasActiveDiagnostic = Flag; }

  void setFoldFailureDiagnostic(bool Flag) override {
    HasFoldFailureDiagnostic = Flag;
  }

  Expr::EvalStatus &getEvalStatus() const override { return EvalStatus; }

  ASTContext &getCtx() const override { return Ctx; }

  // If we have a prior diagnostic, it will be noting that the expression
  // isn't a constant expression. This diagnostic is more important,
  // unless we require this evaluation to produce a constant expression.
  //
  // FIXME: We might want to show both diagnostics to the user in
  // EM_ConstantFold mode.
  bool hasPriorDiagnostic() override {
    if (!EvalStatus.Diag->empty()) {
      switch (EvalMode) {
      case EM_ConstantFold:
      case EM_IgnoreSideEffects:
        if (!HasFoldFailureDiagnostic)
          break;
        // We've already failed to fold something. Keep that diagnostic.
        LLVM_FALLTHROUGH[[gnu::fallthrough]];
      case EM_ConstantExpression:
      case EM_ConstantExpressionUnevaluated:
        setActiveDiagnostic(false);
        return true;
      }
    }
    return false;
  }

  unsigned getCallStackDepth() override { return CallStackDepth; }

public:
  /// Should we continue evaluation after encountering a side-effect that we
  /// couldn't model?
  bool keepEvaluatingAfterSideEffect() {
    switch (EvalMode) {
    case EM_IgnoreSideEffects:
      return true;

    case EM_ConstantExpression:
    case EM_ConstantExpressionUnevaluated:
    case EM_ConstantFold:
      // By default, assume any side effect might be valid in some other
      // evaluation of this expression from a different context.
      return checkingPotentialConstantExpression() ||
             checkingForUndefinedBehavior();
    }
    llvm_unreachable("Missed EvalMode case")__builtin_unreachable();
  }

  /// Note that we have had a side-effect, and determine whether we should
  /// keep evaluating.
  bool noteSideEffect() {
    EvalStatus.HasSideEffects = true;
    return keepEvaluatingAfterSideEffect();
  }

  /// Should we continue evaluation after encountering undefined behavior?
  bool keepEvaluatingAfterUndefinedBehavior() {
    switch (EvalMode) {
    case EM_IgnoreSideEffects:
    case EM_ConstantFold:
      return true;

    case EM_ConstantExpression:
    case EM_ConstantExpressionUnevaluated:
      return checkingForUndefinedBehavior();
    }
    llvm_unreachable("Missed EvalMode case")__builtin_unreachable();
  }

  /// Note that we hit something that was technically undefined behavior, but
  /// that we can evaluate past it (such as signed overflow or floating-point
  /// division by zero.)
  bool noteUndefinedBehavior() override {
    EvalStatus.HasUndefinedBehavior = true;
    return keepEvaluatingAfterUndefinedBehavior();
  }

  /// Should we continue evaluation as much as possible after encountering a
  /// construct which can't be reduced to a value?
  bool keepEvaluatingAfterFailure() const override {
    if (!StepsLeft)
      return false;

    switch (EvalMode) {
    case EM_ConstantExpression:
    case EM_ConstantExpressionUnevaluated:
    case EM_ConstantFold:
    case EM_IgnoreSideEffects:
      return checkingPotentialConstantExpression() ||
             checkingForUndefinedBehavior();
    }
    llvm_unreachable("Missed EvalMode case")__builtin_unreachable();
  }

  /// Notes that we failed to evaluate an expression that other expressions
  /// directly depend on, and determine if we should keep evaluating. This
  /// should only be called if we actually intend to keep evaluating.
  ///
  /// Call noteSideEffect() instead if we may be able to ignore the value that
  /// we failed to evaluate, e.g. if we failed to evaluate Foo() in:
  ///
  /// (Foo(), 1)      // use noteSideEffect
  /// (Foo() || true) // use noteSideEffect
  /// Foo() + 1       // use noteFailure
  LLVM_NODISCARD[[clang::warn_unused_result]] bool noteFailure() {
    // Failure when evaluating some expression often means there is some
    // subexpression whose evaluation was skipped. Therefore, (because we
    // don't track whether we skipped an expression when unwinding after an
    // evaluation failure) every evaluation failure that bubbles up from a
    // subexpression implies that a side-effect has potentially happened. We
    // skip setting the HasSideEffects flag to true until we decide to
    // continue evaluating after that point, which happens here.
    bool KeepGoing = keepEvaluatingAfterFailure();
    EvalStatus.HasSideEffects |= KeepGoing;
    return KeepGoing;
  }

  class ArrayInitLoopIndex {
    EvalInfo &Info;
    uint64_t OuterIndex;

  public:
    ArrayInitLoopIndex(EvalInfo &Info)
        : Info(Info), OuterIndex(Info.ArrayInitIndex) {
      Info.ArrayInitIndex = 0;
    }
    ~ArrayInitLoopIndex() { Info.ArrayInitIndex = OuterIndex; }

    operator uint64_t&() { return Info.ArrayInitIndex; }
  };
};

/// Object used to treat all foldable expressions as constant expressions.
struct FoldConstant {
  EvalInfo &Info;
  bool Enabled;
  bool HadNoPriorDiags;
  EvalInfo::EvaluationMode OldMode;

  explicit FoldConstant(EvalInfo &Info, bool Enabled)
    : Info(Info),
      Enabled(Enabled),
      HadNoPriorDiags(Info.EvalStatus.Diag &&
                      Info.EvalStatus.Diag->empty() &&
                      !Info.EvalStatus.HasSideEffects),
      OldMode(Info.EvalMode) {
    if (Enabled)
      Info.EvalMode = EvalInfo::EM_ConstantFold;
  }
  void keepDiagnostics() { Enabled = false; }
  ~FoldConstant() {
    if (Enabled && HadNoPriorDiags && !Info.EvalStatus.Diag->empty() &&
        !Info.EvalStatus.HasSideEffects)
      Info.EvalStatus.Diag->clear();
    Info.EvalMode = OldMode;
  }
};

/// RAII object used to set the current evaluation mode to ignore
/// side-effects.
struct IgnoreSideEffectsRAII {
  EvalInfo &Info;
  EvalInfo::EvaluationMode OldMode;
  explicit IgnoreSideEffectsRAII(EvalInfo &Info)
      : Info(Info), OldMode(Info.EvalMode) {
    Info.EvalMode = EvalInfo::EM_IgnoreSideEffects;
  }

  ~IgnoreSideEffectsRAII() { Info.EvalMode = OldMode; }
};

/// RAII object used to optionally suppress diagnostics and side-effects from
/// a speculative evaluation.
class SpeculativeEvaluationRAII {
  EvalInfo *Info = nullptr;
  Expr::EvalStatus OldStatus;
  unsigned OldSpeculativeEvaluationDepth;

  void moveFromAndCancel(SpeculativeEvaluationRAII &&Other) {
    Info = Other.Info;
    OldStatus = Other.OldStatus;
    OldSpeculativeEvaluationDepth = Other.OldSpeculativeEvaluationDepth;
    Other.Info = nullptr;
  }

  void maybeRestoreState() {
    if (!Info)
      return;

    Info->EvalStatus = OldStatus;
    Info->SpeculativeEvaluationDepth = OldSpeculativeEvaluationDepth;
  }

public:
  SpeculativeEvaluationRAII() = default;

  SpeculativeEvaluationRAII(
      EvalInfo &Info, SmallVectorImpl<PartialDiagnosticAt> *NewDiag = nullptr)
      : Info(&Info), OldStatus(Info.EvalStatus),
        OldSpeculativeEvaluationDepth(Info.SpeculativeEvaluationDepth) {
    Info.EvalStatus.Diag = NewDiag;
    Info.SpeculativeEvaluationDepth = Info.CallStackDepth + 1;
  }

  SpeculativeEvaluationRAII(const SpeculativeEvaluationRAII &Other) = delete;
  SpeculativeEvaluationRAII(SpeculativeEvaluationRAII &&Other) {
    moveFromAndCancel(std::move(Other));
  }

  SpeculativeEvaluationRAII &operator=(SpeculativeEvaluationRAII &&Other) {
    maybeRestoreState();
    moveFromAndCancel(std::move(Other));
    return *this;
  }

  ~SpeculativeEvaluationRAII() { maybeRestoreState(); }
};

/// RAII object wrapping a full-expression or block scope, and handling
/// the ending of the lifetime of temporaries created within it.
template<ScopeKind Kind>
class ScopeRAII {
  EvalInfo &Info;
  unsigned OldStackSize;
public:
  ScopeRAII(EvalInfo &Info)
      : Info(Info), OldStackSize(Info.CleanupStack.size()) {
    // Push a new temporary version. This is needed to distinguish between
    // temporaries created in different iterations of a loop.
    Info.CurrentCall->pushTempVersion();
  }
  bool destroy(bool RunDestructors = true) {
    bool OK = cleanup(Info, RunDestructors, OldStackSize);
    OldStackSize = -1U;
    return OK;
  }
  ~ScopeRAII() {
    if (OldStackSize != -1U)
      destroy(false);
    // Body moved to a static method to encourage the compiler to inline away
    // instances of this class.
    Info.CurrentCall->popTempVersion();
  }
private:
  static bool cleanup(EvalInfo &Info, bool RunDestructors,
                      unsigned OldStackSize) {
    assert(OldStackSize <= Info.CleanupStack.size() &&((void)0)
           "running cleanups out of order?")((void)0);

    // Run all cleanups for a block scope, and non-lifetime-extended cleanups
    // for a full-expression scope.
    bool Success = true;
    for (unsigned I = Info.CleanupStack.size(); I > OldStackSize; --I) {
      if (Info.CleanupStack[I - 1].isDestroyedAtEndOf(Kind)) {
        if (!Info.CleanupStack[I - 1].endLifetime(Info, RunDestructors)) {
          Success = false;
          break;
        }
      }
    }

    // Compact any retained cleanups.
    auto NewEnd = Info.CleanupStack.begin() + OldStackSize;
    if (Kind != ScopeKind::Block)
      NewEnd =
          std::remove_if(NewEnd, Info.CleanupStack.end(), [](Cleanup &C) {
            return C.isDestroyedAtEndOf(Kind);
          });
    Info.CleanupStack.erase(NewEnd, Info.CleanupStack.end());
    return Success;
  }
};
typedef ScopeRAII<ScopeKind::Block> BlockScopeRAII;
typedef ScopeRAII<ScopeKind::FullExpression> FullExpressionRAII;
typedef ScopeRAII<ScopeKind::Call> CallScopeRAII;
1397}

1399bool SubobjectDesignator::checkSubobject(EvalInfo &Info, const Expr *E,
                                       CheckSubobjectKind CSK) {
if (Invalid)
  return false;
if (isOnePastTheEnd()) {
  Info.CCEDiag(E, diag::note_constexpr_past_end_subobject)
    << CSK;
  setInvalid();
  return false;
}
// Note, we do not diagnose if isMostDerivedAnUnsizedArray(), because there
// must actually be at least one array element; even a VLA cannot have a
// bound of zero. And if our index is nonzero, we already had a CCEDiag.
return true;
1413}

1415void SubobjectDesignator::diagnoseUnsizedArrayPointerArithmetic(EvalInfo &Info,
                                                              const Expr *E) {
Info.CCEDiag(E, diag::note_constexpr_unsized_array_indexed);
// Do not set the designator as invalid: we can represent this situation,
// and correct handling of __builtin_object_size requires us to do so.
1420}

1422void SubobjectDesignator::diagnosePointerArithmetic(EvalInfo &Info,
                                                  const Expr *E,
                                                  const APSInt &N) {
// If we're complaining, we must be able to statically determine the size of
// the most derived array.
if (MostDerivedPathLength == Entries.size() && MostDerivedIsArrayElement)
  Info.CCEDiag(E, diag::note_constexpr_array_index)
    << N << /*array*/ 0
    << static_cast<unsigned>(getMostDerivedArraySize());
else
  Info.CCEDiag(E, diag::note_constexpr_array_index)
    << N << /*non-array*/ 1;
setInvalid();
1435}

1437CallStackFrame::CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
                             const FunctionDecl *Callee, const LValue *This,
                             CallRef Call)
  : Info(Info), Caller(Info.CurrentCall), Callee(Callee), This(This),
    Arguments(Call), CallLoc(CallLoc), Index(Info.NextCallIndex++) {
Info.CurrentCall = this;
++Info.CallStackDepth;
1444}

1446CallStackFrame::~CallStackFrame() {
assert(Info.CurrentCall == this && "calls retired out of order")((void)0);
--Info.CallStackDepth;
Info.CurrentCall = Caller;
1450}

1452static bool isRead(AccessKinds AK) {
return AK == AK_Read || AK == AK_ReadObjectRepresentation;
1454}

1456static bool isModification(AccessKinds AK) {
switch (AK) {
case AK_Read:
case AK_ReadObjectRepresentation:
case AK_MemberCall:
case AK_DynamicCast:
case AK_TypeId:
  return false;
case AK_Assign:
case AK_Increment:
case AK_Decrement:
case AK_Construct:
case AK_Destroy:
  return true;
}
llvm_unreachable("unknown access kind")__builtin_unreachable();
1472}

1474static bool isAnyAccess(AccessKinds AK) {
return isRead(AK) || isModification(AK);
1476}

1478/// Is this an access per the C++ definition?
1479static bool isFormalAccess(AccessKinds AK) {
return isAnyAccess(AK) && AK != AK_Construct && AK != AK_Destroy;
1481}

1483/// Is this kind of axcess valid on an indeterminate object value?
1484static bool isValidIndeterminateAccess(AccessKinds AK) {
switch (AK) {
case AK_Read:
case AK_Increment:
case AK_Decrement:
  // These need the object's value.
  return false;

case AK_ReadObjectRepresentation:
case AK_Assign:
case AK_Construct:
case AK_Destroy:
  // Construction and destruction don't need the value.
  return true;

case AK_MemberCall:
case AK_DynamicCast:
case AK_TypeId:
  // These aren't really meaningful on scalars.
  return true;
}
llvm_unreachable("unknown access kind")__builtin_unreachable();
1506}

1508namespace {
struct ComplexValue {
private:
  bool IsInt;

public:
  APSInt IntReal, IntImag;
  APFloat FloatReal, FloatImag;

  ComplexValue() : FloatReal(APFloat::Bogus()), FloatImag(APFloat::Bogus()) {}

  void makeComplexFloat() { IsInt = false; }
  bool isComplexFloat() const { return !IsInt; }
  APFloat &getComplexFloatReal() { return FloatReal; }
  APFloat &getComplexFloatImag() { return FloatImag; }

  void makeComplexInt() { IsInt = true; }
  bool isComplexInt() const { return IsInt; }
  APSInt &getComplexIntReal() { return IntReal; }
  APSInt &getComplexIntImag() { return IntImag; }

  void moveInto(APValue &v) const {
    if (isComplexFloat())
      v = APValue(FloatReal, FloatImag);
    else
      v = APValue(IntReal, IntImag);
  }
  void setFrom(const APValue &v) {
    assert(v.isComplexFloat() || v.isComplexInt())((void)0);
    if (v.isComplexFloat()) {
      makeComplexFloat();
      FloatReal = v.getComplexFloatReal();
      FloatImag = v.getComplexFloatImag();
    } else {
      makeComplexInt();
      IntReal = v.getComplexIntReal();
      IntImag = v.getComplexIntImag();
    }
  }
};

struct LValue {
  APValue::LValueBase Base;
  CharUnits Offset;
  SubobjectDesignator Designator;
  bool IsNullPtr : 1;
  bool InvalidBase : 1;

  const APValue::LValueBase getLValueBase() const { return Base; }
  CharUnits &getLValueOffset() { return Offset; }
  const CharUnits &getLValueOffset() const { return Offset; }
  SubobjectDesignator &getLValueDesignator() { return Designator; }
  const SubobjectDesignator &getLValueDesignator() const { return Designator;}
  bool isNullPointer() const { return IsNullPtr;}

  unsigned getLValueCallIndex() const { return Base.getCallIndex(); }
  unsigned getLValueVersion() const { return Base.getVersion(); }

  void moveInto(APValue &V) const {
    if (Designator.Invalid)
      V = APValue(Base, Offset, APValue::NoLValuePath(), IsNullPtr);
    else {
      assert(!InvalidBase && "APValues can't handle invalid LValue bases")((void)0);
      V = APValue(Base, Offset, Designator.Entries,
                  Designator.IsOnePastTheEnd, IsNullPtr);
    }
  }
  void setFrom(ASTContext &Ctx, const APValue &V) {
    assert(V.isLValue() && "Setting LValue from a non-LValue?")((void)0);
    Base = V.getLValueBase();
    Offset = V.getLValueOffset();
    InvalidBase = false;
    Designator = SubobjectDesignator(Ctx, V);
    IsNullPtr = V.isNullPointer();
  }

  void set(APValue::LValueBase B, bool BInvalid = false) {
1585#ifndef NDEBUG1
    // We only allow a few types of invalid bases. Enforce that here.
    if (BInvalid) {
      const auto *E = B.get<const Expr *>();
      assert((isa<MemberExpr>(E) || tryUnwrapAllocSizeCall(E)) &&((void)0)
             "Unexpected type of invalid base")((void)0);
    }
1592#endif

    Base = B;
    Offset = CharUnits::fromQuantity(0);
    InvalidBase = BInvalid;
    Designator = SubobjectDesignator(getType(B));
    IsNullPtr = false;
  }

  void setNull(ASTContext &Ctx, QualType PointerTy) {
    Base = (const ValueDecl *)nullptr;
    Offset =
        CharUnits::fromQuantity(Ctx.getTargetNullPointerValue(PointerTy));
    InvalidBase = false;
    Designator = SubobjectDesignator(PointerTy->getPointeeType());
    IsNullPtr = true;
  }

  void setInvalid(APValue::LValueBase B, unsigned I = 0) {
    set(B, true);
  }

  std::string toString(ASTContext &Ctx, QualType T) const {
    APValue Printable;
    moveInto(Printable);
    return Printable.getAsString(Ctx, T);
  }

private:
  // Check that this LValue is not based on a null pointer. If it is, produce
  // a diagnostic and mark the designator as invalid.
  template <typename GenDiagType>
  bool checkNullPointerDiagnosingWith(const GenDiagType &GenDiag) {
    if (Designator.Invalid)
      return false;
    if (IsNullPtr) {
      GenDiag();
      Designator.setInvalid();
      return false;
    }
    return true;
  }

public:
  bool checkNullPointer(EvalInfo &Info, const Expr *E,
                        CheckSubobjectKind CSK) {
    return checkNullPointerDiagnosingWith([&Info, E, CSK] {
      Info.CCEDiag(E, diag::note_constexpr_null_subobject) << CSK;
    });
  }

  bool checkNullPointerForFoldAccess(EvalInfo &Info, const Expr *E,
                                     AccessKinds AK) {
    return checkNullPointerDiagnosingWith([&Info, E, AK] {
      Info.FFDiag(E, diag::note_constexpr_access_null) << AK;
    });
  }

  // Check this LValue refers to an object. If not, set the designator to be
  // invalid and emit a diagnostic.
  bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK) {
    return (CSK == CSK_ArrayToPointer || checkNullPointer(Info, E, CSK)) &&
           Designator.checkSubobject(Info, E, CSK);
  }

  void addDecl(EvalInfo &Info, const Expr *E,
               const Decl *D, bool Virtual = false) {
    if (checkSubobject(Info, E, isa<FieldDecl>(D) ? CSK_Field : CSK_Base))
      Designator.addDeclUnchecked(D, Virtual);
  }
  void addUnsizedArray(EvalInfo &Info, const Expr *E, QualType ElemTy) {
    if (!Designator.Entries.empty()) {
      Info.CCEDiag(E, diag::note_constexpr_unsupported_unsized_array);
      Designator.setInvalid();
      return;
    }
    if (checkSubobject(Info, E, CSK_ArrayToPointer)) {
      assert(getType(Base)->isPointerType() || getType(Base)->isArrayType())((void)0);
      Designator.FirstEntryIsAnUnsizedArray = true;
      Designator.addUnsizedArrayUnchecked(ElemTy);
    }
  }
  void addArray(EvalInfo &Info, const Expr *E, const ConstantArrayType *CAT) {
    if (checkSubobject(Info, E, CSK_ArrayToPointer))
      Designator.addArrayUnchecked(CAT);
  }
  void addComplex(EvalInfo &Info, const Expr *E, QualType EltTy, bool Imag) {
    if (checkSubobject(Info, E, Imag ? CSK_Imag : CSK_Real))
      Designator.addComplexUnchecked(EltTy, Imag);
  }
  void clearIsNullPointer() {
    IsNullPtr = false;
  }
  void adjustOffsetAndIndex(EvalInfo &Info, const Expr *E,
                            const APSInt &Index, CharUnits ElementSize) {
    // An index of 0 has no effect. (In C, adding 0 to a null pointer is UB,
    // but we're not required to diagnose it and it's valid in C++.)
    if (!Index)
      return;

    // Compute the new offset in the appropriate width, wrapping at 64 bits.
    // FIXME: When compiling for a 32-bit target, we should use 32-bit
    // offsets.
    uint64_t Offset64 = Offset.getQuantity();
    uint64_t ElemSize64 = ElementSize.getQuantity();
    uint64_t Index64 = Index.extOrTrunc(64).getZExtValue();
    Offset = CharUnits::fromQuantity(Offset64 + ElemSize64 * Index64);

    if (checkNullPointer(Info, E, CSK_ArrayIndex))
      Designator.adjustIndex(Info, E, Index);
    clearIsNullPointer();
  }
  void adjustOffset(CharUnits N) {
    Offset += N;
    if (N.getQuantity())
      clearIsNullPointer();
  }
};

struct MemberPtr {
  MemberPtr() {}
  explicit MemberPtr(const ValueDecl *Decl) :
    DeclAndIsDerivedMember(Decl, false), Path() {}

  /// The member or (direct or indirect) field referred to by this member
  /// pointer, or 0 if this is a null member pointer.
  const ValueDecl *getDecl() const {
    return DeclAndIsDerivedMember.getPointer();
  }
  /// Is this actually a member of some type derived from the relevant class?
  bool isDerivedMember() const {
    return DeclAndIsDerivedMember.getInt();
  }
  /// Get the class which the declaration actually lives in.
  const CXXRecordDecl *getContainingRecord() const {
    return cast<CXXRecordDecl>(
        DeclAndIsDerivedMember.getPointer()->getDeclContext());
  }

  void moveInto(APValue &V) const {
    V = APValue(getDecl(), isDerivedMember(), Path);
  }
  void setFrom(const APValue &V) {
    assert(V.isMemberPointer())((void)0);
    DeclAndIsDerivedMember.setPointer(V.getMemberPointerDecl());
    DeclAndIsDerivedMember.setInt(V.isMemberPointerToDerivedMember());
    Path.clear();
    ArrayRef<const CXXRecordDecl*> P = V.getMemberPointerPath();
    Path.insert(Path.end(), P.begin(), P.end());
  }

  /// DeclAndIsDerivedMember - The member declaration, and a flag indicating
  /// whether the member is a member of some class derived from the class type
  /// of the member pointer.
  llvm::PointerIntPair<const ValueDecl*, 1, bool> DeclAndIsDerivedMember;
  /// Path - The path of base/derived classes from the member declaration's
  /// class (exclusive) to the class type of the member pointer (inclusive).
  SmallVector<const CXXRecordDecl*, 4> Path;

  /// Perform a cast towards the class of the Decl (either up or down the
  /// hierarchy).
  bool castBack(const CXXRecordDecl *Class) {
    assert(!Path.empty())((void)0);
    const CXXRecordDecl *Expected;
    if (Path.size() >= 2)
      Expected = Path[Path.size() - 2];
    else
      Expected = getContainingRecord();
    if (Expected->getCanonicalDecl() != Class->getCanonicalDecl()) {
      // C++11 [expr.static.cast]p12: In a conversion from (D::*) to (B::*),
      // if B does not contain the original member and is not a base or
      // derived class of the class containing the original member, the result
      // of the cast is undefined.
      // C++11 [conv.mem]p2 does not cover this case for a cast from (B::*) to
      // (D::*). We consider that to be a language defect.
      return false;
    }
    Path.pop_back();
    return true;
  }
  /// Perform a base-to-derived member pointer cast.
  bool castToDerived(const CXXRecordDecl *Derived) {
    if (!getDecl())
      return true;
    if (!isDerivedMember()) {
      Path.push_back(Derived);
      return true;
    }
    if (!castBack(Derived))
      return false;
    if (Path.empty())
      DeclAndIsDerivedMember.setInt(false);
    return true;
  }
  /// Perform a derived-to-base member pointer cast.
  bool castToBase(const CXXRecordDecl *Base) {
    if (!getDecl())
      return true;
    if (Path.empty())
      DeclAndIsDerivedMember.setInt(true);
    if (isDerivedMember()) {
      Path.push_back(Base);
      return true;
    }
    return castBack(Base);
  }
};

/// Compare two member pointers, which are assumed to be of the same type.
static bool operator==(const MemberPtr &LHS, const MemberPtr &RHS) {
  if (!LHS.getDecl() || !RHS.getDecl())
    return !LHS.getDecl() && !RHS.getDecl();
  if (LHS.getDecl()->getCanonicalDecl() != RHS.getDecl()->getCanonicalDecl())
    return false;
  return LHS.Path == RHS.Path;
}
1808}

1810static bool Evaluate(APValue &Result, EvalInfo &Info, const Expr *E);
1811static bool EvaluateInPlace(APValue &Result, EvalInfo &Info,
                          const LValue &This, const Expr *E,
                          bool AllowNonLiteralTypes = false);
1814static bool EvaluateLValue(const Expr *E, LValue &Result, EvalInfo &Info,
                         bool InvalidBaseOK = false);
1816static bool EvaluatePointer(const Expr *E, LValue &Result, EvalInfo &Info,
                          bool InvalidBaseOK = false);
1818static bool EvaluateMemberPointer(const Expr *E, MemberPtr &Result,
                                EvalInfo &Info);
1820static bool EvaluateTemporary(const Expr *E, LValue &Result, EvalInfo &Info);
1821static bool EvaluateInteger(const Expr *E, APSInt &Result, EvalInfo &Info);
1822static bool EvaluateIntegerOrLValue(const Expr *E, APValue &Result,
                                  EvalInfo &Info);
1824static bool EvaluateFloat(const Expr *E, APFloat &Result, EvalInfo &Info);
1825static bool EvaluateComplex(const Expr *E, ComplexValue &Res, EvalInfo &Info);
1826static bool EvaluateAtomic(const Expr *E, const LValue *This, APValue &Result,
                         EvalInfo &Info);
1828static bool EvaluateAsRValue(EvalInfo &Info, const Expr *E, APValue &Result);

1830/// Evaluate an integer or fixed point expression into an APResult.
1831static bool EvaluateFixedPointOrInteger(const Expr *E, APFixedPoint &Result,
                                      EvalInfo &Info);

1834/// Evaluate only a fixed point expression into an APResult.
1835static bool EvaluateFixedPoint(const Expr *E, APFixedPoint &Result,
                             EvalInfo &Info);

1838//===----------------------------------------------------------------------===//
1839// Misc utilities
1840//===----------------------------------------------------------------------===//

1842/// Negate an APSInt in place, converting it to a signed form if necessary, and
1843/// preserving its value (by extending by up to one bit as needed).
1844static void negateAsSigned(APSInt &Int) {
if (Int.isUnsigned() || Int.isMinSignedValue()) {
  Int = Int.extend(Int.getBitWidth() + 1);
  Int.setIsSigned(true);
}
Int = -Int;
1850}

1852template<typename KeyT>
1853APValue &CallStackFrame::createTemporary(const KeyT *Key, QualType T,
                                       ScopeKind Scope, LValue &LV) {
unsigned Version = getTempVersion();
APValue::LValueBase Base(Key, Index, Version);
LV.set(Base);
return createLocal(Base, Key, T, Scope);
1859}

1861/// Allocate storage for a parameter of a function call made in this frame.
1862APValue &CallStackFrame::createParam(CallRef Args, const ParmVarDecl *PVD,
                                   LValue &LV) {
assert(Args.CallIndex == Index && "creating parameter in wrong frame")((void)0);
APValue::LValueBase Base(PVD, Index, Args.Version);
LV.set(Base);
// We always destroy parameters at the end of the call, even if we'd allow
// them to live to the end of the full-expression at runtime, in order to
// give portable results and match other compilers.
return createLocal(Base, PVD, PVD->getType(), ScopeKind::Call);
1871}

1873APValue &CallStackFrame::createLocal(APValue::LValueBase Base, const void *Key,
                                   QualType T, ScopeKind Scope) {
assert(Base.getCallIndex() == Index && "lvalue for wrong frame")((void)0);
unsigned Version = Base.getVersion();
APValue &Result = Temporaries[MapKeyTy(Key, Version)];
assert(Result.isAbsent() && "local created multiple times")((void)0);

// If we're creating a local immediately in the operand of a speculative
// evaluation, don't register a cleanup to be run outside the speculative
// evaluation context, since we won't actually be able to initialize this
// object.
if (Index <= Info.SpeculativeEvaluationDepth) {
  if (T.isDestructedType())
    Info.noteSideEffect();
} else {
  Info.CleanupStack.push_back(Cleanup(&Result, Base, T, Scope));
}
return Result;
1891}

1893APValue *EvalInfo::createHeapAlloc(const Expr *E, QualType T, LValue &LV) {
if (NumHeapAllocs > DynamicAllocLValue::getMaxIndex()) {
  FFDiag(E, diag::note_constexpr_heap_alloc_limit_exceeded);
  return nullptr;
}

DynamicAllocLValue DA(NumHeapAllocs++);
LV.set(APValue::LValueBase::getDynamicAlloc(DA, T));
auto Result = HeapAllocs.emplace(std::piecewise_construct,
                                 std::forward_as_tuple(DA), std::tuple<>());
assert(Result.second && "reused a heap alloc index?")((void)0);
Result.first->second.AllocExpr = E;
return &Result.first->second.Value;
1906}

1908/// Produce a string describing the given constexpr call.
1909void CallStackFrame::describe(raw_ostream &Out) {
unsigned ArgIndex = 0;
bool IsMemberCall = isa<CXXMethodDecl>(Callee) &&
                    !isa<CXXConstructorDecl>(Callee) &&
                    cast<CXXMethodDecl>(Callee)->isInstance();

if (!IsMemberCall)
  Out << *Callee << '(';

if (This && IsMemberCall) {
  APValue Val;
  This->moveInto(Val);
  Val.printPretty(Out, Info.Ctx,
                  This->Designator.MostDerivedType);
  // FIXME: Add parens around Val if needed.
  Out << "->" << *Callee << '(';
  IsMemberCall = false;
}

for (FunctionDecl::param_const_iterator I = Callee->param_begin(),
     E = Callee->param_end(); I != E; ++I, ++ArgIndex) {
  if (ArgIndex > (unsigned)IsMemberCall)
    Out << ", ";

  const ParmVarDecl *Param = *I;
  APValue *V = Info.getParamSlot(Arguments, Param);
  if (V)
    V->printPretty(Out, Info.Ctx, Param->getType());
  else
    Out << "<...>";

  if (ArgIndex == 0 && IsMemberCall)
    Out << "->" << *Callee << '(';
}

Out << ')';
1945}

1947/// Evaluate an expression to see if it had side-effects, and discard its
1948/// result.
1949/// \return \c true if the caller should keep evaluating.
1950static bool EvaluateIgnoredValue(EvalInfo &Info, const Expr *E) {
assert(!E->isValueDependent())((void)0);
APValue Scratch;
if (!Evaluate(Scratch, Info, E))
  // We don't need the value, but we might have skipped a side effect here.
  return Info.noteSideEffect();
return true;
1957}

1959/// Should this call expression be treated as a string literal?
1960static bool IsStringLiteralCall(const CallExpr *E) {
unsigned Builtin = E->getBuiltinCallee();
return (Builtin == Builtin::BI__builtin___CFStringMakeConstantString ||
        Builtin == Builtin::BI__builtin___NSStringMakeConstantString);
1964}

1966static bool IsGlobalLValue(APValue::LValueBase B) {
// C++11 [expr.const]p3 An address constant expression is a prvalue core
// constant expression of pointer type that evaluates to...

// ... a null pointer value, or a prvalue core constant expression of type
// std::nullptr_t.
if (!B) return true;

if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>()) {
  // ... the address of an object with static storage duration,
  if (const VarDecl *VD = dyn_cast<VarDecl>(D))
    return VD->hasGlobalStorage();
  if (isa<TemplateParamObjectDecl>(D))
    return true;
  // ... the address of a function,
  // ... the address of a GUID [MS extension],
  return isa<FunctionDecl>(D) || isa<MSGuidDecl>(D);
}

if (B.is<TypeInfoLValue>() || B.is<DynamicAllocLValue>())
  return true;

const Expr *E = B.get<const Expr*>();
switch (E->getStmtClass()) {
default:
  return false;
case Expr::CompoundLiteralExprClass: {
  const CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
  return CLE->isFileScope() && CLE->isLValue();
}
case Expr::MaterializeTemporaryExprClass:
  // A materialized temporary might have been lifetime-extended to static
  // storage duration.
  return cast<MaterializeTemporaryExpr>(E)->getStorageDuration() == SD_Static;
// A string literal has static storage duration.
case Expr::StringLiteralClass:
case Expr::PredefinedExprClass:
case Expr::ObjCStringLiteralClass:
case Expr::ObjCEncodeExprClass:
  return true;
case Expr::ObjCBoxedExprClass:
  return cast<ObjCBoxedExpr>(E)->isExpressibleAsConstantInitializer();
case Expr::CallExprClass:
  return IsStringLiteralCall(cast<CallExpr>(E));
// For GCC compatibility, &&label has static storage duration.
case Expr::AddrLabelExprClass:
  return true;
// A Block literal expression may be used as the initialization value for
// Block variables at global or local static scope.
case Expr::BlockExprClass:
  return !cast<BlockExpr>(E)->getBlockDecl()->hasCaptures();
case Expr::ImplicitValueInitExprClass:
  // FIXME:
  // We can never form an lvalue with an implicit value initialization as its
  // base through expression evaluation, so these only appear in one case: the
  // implicit variable declaration we invent when checking whether a constexpr
  // constructor can produce a constant expression. We must assume that such
  // an expression might be a global lvalue.
  return true;
}
2026}

2028static const ValueDecl *GetLValueBaseDecl(const LValue &LVal) {
return LVal.Base.dyn_cast<const ValueDecl*>();
2030}

2032static bool IsLiteralLValue(const LValue &Value) {
if (Value.getLValueCallIndex())
  return false;
const Expr *E = Value.Base.dyn_cast<const Expr*>();
return E && !isa<MaterializeTemporaryExpr>(E);
2037}

2039static bool IsWeakLValue(const LValue &Value) {
const ValueDecl *Decl = GetLValueBaseDecl(Value);
return Decl && Decl->isWeak();
2042}

2044static bool isZeroSized(const LValue &Value) {
const ValueDecl *Decl = GetLValueBaseDecl(Value);
if (Decl && isa<VarDecl>(Decl)) {
  QualType Ty = Decl->getType();
  if (Ty->isArrayType())
    return Ty->isIncompleteType() ||
           Decl->getASTContext().getTypeSize(Ty) == 0;
}
return false;
2053}

2055static bool HasSameBase(const LValue &A, const LValue &B) {
if (!A.getLValueBase())
  return !B.getLValueBase();
if (!B.getLValueBase())
  return false;

if (A.getLValueBase().getOpaqueValue() !=
    B.getLValueBase().getOpaqueValue())
  return false;

return A.getLValueCallIndex() == B.getLValueCallIndex() &&
       A.getLValueVersion() == B.getLValueVersion();
2067}

2069static void NoteLValueLocation(EvalInfo &Info, APValue::LValueBase Base) {
assert(Base && "no location for a null lvalue")((void)0);
const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();

// For a parameter, find the corresponding call stack frame (if it still
// exists), and point at the parameter of the function definition we actually
// invoked.
if (auto *PVD = dyn_cast_or_null<ParmVarDecl>(VD)) {
  unsigned Idx = PVD->getFunctionScopeIndex();
  for (CallStackFrame *F = Info.CurrentCall; F; F = F->Caller) {
    if (F->Arguments.CallIndex == Base.getCallIndex() &&
        F->Arguments.Version == Base.getVersion() && F->Callee &&
        Idx < F->Callee->getNumParams()) {
      VD = F->Callee->getParamDecl(Idx);
      break;
    }
  }
}

if (VD)
  Info.Note(VD->getLocation(), diag::note_declared_at);
else if (const Expr *E = Base.dyn_cast<const Expr*>())
  Info.Note(E->getExprLoc(), diag::note_constexpr_temporary_here);
else if (DynamicAllocLValue DA = Base.dyn_cast<DynamicAllocLValue>()) {
  // FIXME: Produce a note for dangling pointers too.
  if (Optional<DynAlloc*> Alloc = Info.lookupDynamicAlloc(DA))
    Info.Note((*Alloc)->AllocExpr->getExprLoc(),
              diag::note_constexpr_dynamic_alloc_here);
}
// We have no information to show for a typeid(T) object.
2099}

2101enum class CheckEvaluationResultKind {
ConstantExpression,
FullyInitialized,
2104};

2106/// Materialized temporaries that we've already checked to determine if they're
2107/// initializsed by a constant expression.
2108using CheckedTemporaries =
  llvm::SmallPtrSet<const MaterializeTemporaryExpr *, 8>;

2111static bool CheckEvaluationResult(CheckEvaluationResultKind CERK,
                                EvalInfo &Info, SourceLocation DiagLoc,
                                QualType Type, const APValue &Value,
                                ConstantExprKind Kind,
                                SourceLocation SubobjectLoc,
                                CheckedTemporaries &CheckedTemps);

2118/// Check that this reference or pointer core constant expression is a valid
2119/// value for an address or reference constant expression. Return true if we
2120/// can fold this expression, whether or not it's a constant expression.
2121static bool CheckLValueConstantExpression(EvalInfo &Info, SourceLocation Loc,
                                        QualType Type, const LValue &LVal,
                                        ConstantExprKind Kind,
                                        CheckedTemporaries &CheckedTemps) {
bool IsReferenceType = Type->isReferenceType();

APValue::LValueBase Base = LVal.getLValueBase();
const SubobjectDesignator &Designator = LVal.getLValueDesignator();

const Expr *BaseE = Base.dyn_cast<const Expr *>();
const ValueDecl *BaseVD = Base.dyn_cast<const ValueDecl*>();

// Additional restrictions apply in a template argument. We only enforce the
// C++20 restrictions here; additional syntactic and semantic restrictions
// are applied elsewhere.
if (isTemplateArgument(Kind)) {
  int InvalidBaseKind = -1;
  StringRef Ident;
  if (Base.is<TypeInfoLValue>())
    InvalidBaseKind = 0;
  else if (isa_and_nonnull<StringLiteral>(BaseE))
    InvalidBaseKind = 1;
  else if (isa_and_nonnull<MaterializeTemporaryExpr>(BaseE) ||
           isa_and_nonnull<LifetimeExtendedTemporaryDecl>(BaseVD))
    InvalidBaseKind = 2;
  else if (auto *PE = dyn_cast_or_null<PredefinedExpr>(BaseE)) {
    InvalidBaseKind = 3;
    Ident = PE->getIdentKindName();
  }

  if (InvalidBaseKind != -1) {
    Info.FFDiag(Loc, diag::note_constexpr_invalid_template_arg)
        << IsReferenceType << !Designator.Entries.empty() << InvalidBaseKind
        << Ident;
    return false;
  }
}

if (auto *FD = dyn_cast_or_null<FunctionDecl>(BaseVD)) {
  if (FD->isConsteval()) {
    Info.FFDiag(Loc, diag::note_consteval_address_accessible)
        << !Type->isAnyPointerType();
    Info.Note(FD->getLocation(), diag::note_declared_at);
    return false;
  }
}

// Check that the object is a global. Note that the fake 'this' object we
// manufacture when checking potential constant expressions is conservatively
// assumed to be global here.
if (!IsGlobalLValue(Base)) {
  if (Info.getLangOpts().CPlusPlus11) {
    const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
    Info.FFDiag(Loc, diag::note_constexpr_non_global, 1)
      << IsReferenceType << !Designator.Entries.empty()
      << !!VD << VD;

    auto *VarD = dyn_cast_or_null<VarDecl>(VD);
    if (VarD && VarD->isConstexpr()) {
      // Non-static local constexpr variables have unintuitive semantics:
      //   constexpr int a = 1;
      //   constexpr const int *p = &a;
      // ... is invalid because the address of 'a' is not constant. Suggest
      // adding a 'static' in this case.
      Info.Note(VarD->getLocation(), diag::note_constexpr_not_static)
          << VarD
          << FixItHint::CreateInsertion(VarD->getBeginLoc(), "static ");
    } else {
      NoteLValueLocation(Info, Base);
    }
  } else {
    Info.FFDiag(Loc);
  }
  // Don't allow references to temporaries to escape.
  return false;
}
assert((Info.checkingPotentialConstantExpression() ||((void)0)
        LVal.getLValueCallIndex() == 0) &&((void)0)
       "have call index for global lvalue")((void)0);

if (Base.is<DynamicAllocLValue>()) {
  Info.FFDiag(Loc, diag::note_constexpr_dynamic_alloc)
      << IsReferenceType << !Designator.Entries.empty();
  NoteLValueLocation(Info, Base);
  return false;
}

if (BaseVD) {
  if (const VarDecl *Var = dyn_cast<const VarDecl>(BaseVD)) {
    // Check if this is a thread-local variable.
    if (Var->getTLSKind())
      // FIXME: Diagnostic!
      return false;

    // A dllimport variable never acts like a constant, unless we're
    // evaluating a value for use only in name mangling.
    if (!isForManglingOnly(Kind) && Var->hasAttr<DLLImportAttr>())
      // FIXME: Diagnostic!
      return false;
  }
  if (const auto *FD = dyn_cast<const FunctionDecl>(BaseVD)) {
    // __declspec(dllimport) must be handled very carefully:
    // We must never initialize an expression with the thunk in C++.
    // Doing otherwise would allow the same id-expression to yield
    // different addresses for the same function in different translation
    // units.  However, this means that we must dynamically initialize the
    // expression with the contents of the import address table at runtime.
    //
    // The C language has no notion of ODR; furthermore, it has no notion of
    // dynamic initialization.  This means that we are permitted to
    // perform initialization with the address of the thunk.
    if (Info.getLangOpts().CPlusPlus && !isForManglingOnly(Kind) &&
        FD->hasAttr<DLLImportAttr>())
      // FIXME: Diagnostic!
      return false;
  }
} else if (const auto *MTE =
               dyn_cast_or_null<MaterializeTemporaryExpr>(BaseE)) {
  if (CheckedTemps.insert(MTE).second) {
    QualType TempType = getType(Base);
    if (TempType.isDestructedType()) {
      Info.FFDiag(MTE->getExprLoc(),
                  diag::note_constexpr_unsupported_temporary_nontrivial_dtor)
          << TempType;
      return false;
    }

    APValue *V = MTE->getOrCreateValue(false);
    assert(V && "evasluation result refers to uninitialised temporary")((void)0);
    if (!CheckEvaluationResult(CheckEvaluationResultKind::ConstantExpression,
                               Info, MTE->getExprLoc(), TempType, *V,
                               Kind, SourceLocation(), CheckedTemps))
      return false;
  }
}

// Allow address constant expressions to be past-the-end pointers. This is
// an extension: the standard requires them to point to an object.
if (!IsReferenceType)
  return true;

// A reference constant expression must refer to an object.
if (!Base) {
  // FIXME: diagnostic
  Info.CCEDiag(Loc);
  return true;
}

// Does this refer one past the end of some object?
if (!Designator.Invalid && Designator.isOnePastTheEnd()) {
  Info.FFDiag(Loc, diag::note_constexpr_past_end, 1)
    << !Designator.Entries.empty() << !!BaseVD << BaseVD;
  NoteLValueLocation(Info, Base);
}

return true;
2277}

2279/// Member pointers are constant expressions unless they point to a
2280/// non-virtual dllimport member function.
2281static bool CheckMemberPointerConstantExpression(EvalInfo &Info,
                                               SourceLocation Loc,
                                               QualType Type,
                                               const APValue &Value,
                                               ConstantExprKind Kind) {
const ValueDecl *Member = Value.getMemberPointerDecl();
const auto *FD = dyn_cast_or_null<CXXMethodDecl>(Member);
if (!FD)
  return true;
if (FD->isConsteval()) {
  Info.FFDiag(Loc, diag::note_consteval_address_accessible) << /*pointer*/ 0;
  Info.Note(FD->getLocation(), diag::note_declared_at);
  return false;
}
return isForManglingOnly(Kind) || FD->isVirtual() ||
       !FD->hasAttr<DLLImportAttr>();
2297}

2299/// Check that this core constant expression is of literal type, and if not,
2300/// produce an appropriate diagnostic.
2301static bool CheckLiteralType(EvalInfo &Info, const Expr *E,
                           const LValue *This = nullptr) {
if (!E->isPRValue() || E->getType()->isLiteralType(Info.Ctx))
  return true;

// C++1y: A constant initializer for an object o [...] may also invoke
// constexpr constructors for o and its subobjects even if those objects
// are of non-literal class types.
//
// C++11 missed this detail for aggregates, so classes like this:
//   struct foo_t { union { int i; volatile int j; } u; };
// are not (obviously) initializable like so:
//   __attribute__((__require_constant_initialization__))
//   static const foo_t x = {{0}};
// because "i" is a subobject with non-literal initialization (due to the
// volatile member of the union). See:
//   http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1677
// Therefore, we use the C++1y behavior.
if (This && Info.EvaluatingDecl == This->getLValueBase())
  return true;

// Prvalue constant expressions must be of literal types.
if (Info.getLangOpts().CPlusPlus11)
  Info.FFDiag(E, diag::note_constexpr_nonliteral)
    << E->getType();
else
  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
return false;
2329}

2331static bool CheckEvaluationResult(CheckEvaluationResultKind CERK,
                                EvalInfo &Info, SourceLocation DiagLoc,
                                QualType Type, const APValue &Value,
                                ConstantExprKind Kind,
                                SourceLocation SubobjectLoc,
                                CheckedTemporaries &CheckedTemps) {
if (!Value.hasValue()) {
  Info.FFDiag(DiagLoc, diag::note_constexpr_uninitialized)
    << true << Type;
  if (SubobjectLoc.isValid())
    Info.Note(SubobjectLoc, diag::note_constexpr_subobject_declared_here);
  return false;
}

// We allow _Atomic(T) to be initialized from anything that T can be
// initialized from.
if (const AtomicType *AT = Type->getAs<AtomicType>())
  Type = AT->getValueType();

// Core issue 1454: For a literal constant expression of array or class type,
// each subobject of its value shall have been initialized by a constant
// expression.
if (Value.isArray()) {
  QualType EltTy = Type->castAsArrayTypeUnsafe()->getElementType();
  for (unsigned I = 0, N = Value.getArrayInitializedElts(); I != N; ++I) {
    if (!CheckEvaluationResult(CERK, Info, DiagLoc, EltTy,
                               Value.getArrayInitializedElt(I), Kind,
                               SubobjectLoc, CheckedTemps))
      return false;
  }
  if (!Value.hasArrayFiller())
    return true;
  return CheckEvaluationResult(CERK, Info, DiagLoc, EltTy,
                               Value.getArrayFiller(), Kind, SubobjectLoc,
                               CheckedTemps);
}
if (Value.isUnion() && Value.getUnionField()) {
  return CheckEvaluationResult(
      CERK, Info, DiagLoc, Value.getUnionField()->getType(),
      Value.getUnionValue(), Kind, Value.getUnionField()->getLocation(),
      CheckedTemps);
}
if (Value.isStruct()) {
  RecordDecl *RD = Type->castAs<RecordType>()->getDecl();
  if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) {
    unsigned BaseIndex = 0;
    for (const CXXBaseSpecifier &BS : CD->bases()) {
      if (!CheckEvaluationResult(CERK, Info, DiagLoc, BS.getType(),
                                 Value.getStructBase(BaseIndex), Kind,
                                 BS.getBeginLoc(), CheckedTemps))
        return false;
      ++BaseIndex;
    }
  }
  for (const auto *I : RD->fields()) {
    if (I->isUnnamedBitfield())
      continue;

    if (!CheckEvaluationResult(CERK, Info, DiagLoc, I->getType(),
                               Value.getStructField(I->getFieldIndex()),
                               Kind, I->getLocation(), CheckedTemps))
      return false;
  }
}

if (Value.isLValue() &&
    CERK == CheckEvaluationResultKind::ConstantExpression) {
  LValue LVal;
  LVal.setFrom(Info.Ctx, Value);
  return CheckLValueConstantExpression(Info, DiagLoc, Type, LVal, Kind,
                                       CheckedTemps);
}

if (Value.isMemberPointer() &&
    CERK == CheckEvaluationResultKind::ConstantExpression)
  return CheckMemberPointerConstantExpression(Info, DiagLoc, Type, Value, Kind);

// Everything else is fine.
return true;
2410}

2412/// Check that this core constant expression value is a valid value for a
2413/// constant expression. If not, report an appropriate diagnostic. Does not
2414/// check that the expression is of literal type.
2415static bool CheckConstantExpression(EvalInfo &Info, SourceLocation DiagLoc,
                                  QualType Type, const APValue &Value,
                                  ConstantExprKind Kind) {
// Nothing to check for a constant expression of type 'cv void'.
if (Type->isVoidType())
  return true;

CheckedTemporaries CheckedTemps;
return CheckEvaluationResult(CheckEvaluationResultKind::ConstantExpression,
                             Info, DiagLoc, Type, Value, Kind,
                             SourceLocation(), CheckedTemps);
2426}

2428/// Check that this evaluated value is fully-initialized and can be loaded by
2429/// an lvalue-to-rvalue conversion.
2430static bool CheckFullyInitialized(EvalInfo &Info, SourceLocation DiagLoc,
                                QualType Type, const APValue &Value) {
CheckedTemporaries CheckedTemps;
return CheckEvaluationResult(
    CheckEvaluationResultKind::FullyInitialized, Info, DiagLoc, Type, Value,
    ConstantExprKind::Normal, SourceLocation(), CheckedTemps);
2436}

2438/// Enforce C++2a [expr.const]/4.17, which disallows new-expressions unless
2439/// "the allocated storage is deallocated within the evaluation".
2440static bool CheckMemoryLeaks(EvalInfo &Info) {
if (!Info.HeapAllocs.empty()) {
  // We can still fold to a constant despite a compile-time memory leak,
  // so long as the heap allocation isn't referenced in the result (we check
  // that in CheckConstantExpression).
  Info.CCEDiag(Info.HeapAllocs.begin()->second.AllocExpr,
               diag::note_constexpr_memory_leak)
      << unsigned(Info.HeapAllocs.size() - 1);
}
return true;
2450}

2452static bool EvalPointerValueAsBool(const APValue &Value, bool &Result) {
// A null base expression indicates a null pointer.  These are always
// evaluatable, and they are false unless the offset is zero.
if (!Value.getLValueBase()) {
  Result = !Value.getLValueOffset().isZero();
  return true;
}

// We have a non-null base.  These are generally known to be true, but if it's
// a weak declaration it can be null at runtime.
Result = true;
const ValueDecl *Decl = Value.getLValueBase().dyn_cast<const ValueDecl*>();
return !Decl || !Decl->isWeak();
2465}

2467static bool HandleConversionToBool(const APValue &Val, bool &Result) {
switch (Val.getKind()) {
case APValue::None:
case APValue::Indeterminate:
  return false;
case APValue::Int:
  Result = Val.getInt().getBoolValue();
  return true;
case APValue::FixedPoint:
  Result = Val.getFixedPoint().getBoolValue();
  return true;
case APValue::Float:
  Result = !Val.getFloat().isZero();
  return true;
case APValue::ComplexInt:
  Result = Val.getComplexIntReal().getBoolValue() ||
           Val.getComplexIntImag().getBoolValue();
  return true;
case APValue::ComplexFloat:
  Result = !Val.getComplexFloatReal().isZero() ||
           !Val.getComplexFloatImag().isZero();
  return true;
case APValue::LValue:
  return EvalPointerValueAsBool(Val, Result);
case APValue::MemberPointer:
  Result = Val.getMemberPointerDecl();
  return true;
case APValue::Vector:
case APValue::Array:
case APValue::Struct:
case APValue::Union:
case APValue::AddrLabelDiff:
  return false;
}

llvm_unreachable("unknown APValue kind")__builtin_unreachable();
2503}

2505static bool EvaluateAsBooleanCondition(const Expr *E, bool &Result,
                                     EvalInfo &Info) {
assert(!E->isValueDependent())((void)0);
assert(E->isPRValue() && "missing lvalue-to-rvalue conv in bool condition")((void)0);
APValue Val;
if (!Evaluate(Val, Info, E))
  return false;
return HandleConversionToBool(Val, Result);
2513}

2515template<typename T>
2516static bool HandleOverflow(EvalInfo &Info, const Expr *E,
                         const T &SrcValue, QualType DestType) {
Info.CCEDiag(E, diag::note_constexpr_overflow)
  << SrcValue << DestType;
return Info.noteUndefinedBehavior();
2521}

2523static bool HandleFloatToIntCast(EvalInfo &Info, const Expr *E,
                               QualType SrcType, const APFloat &Value,
                               QualType DestType, APSInt &Result) {
unsigned DestWidth = Info.Ctx.getIntWidth(DestType);
// Determine whether we are converting to unsigned or signed.
bool DestSigned = DestType->isSignedIntegerOrEnumerationType();

Result = APSInt(DestWidth, !DestSigned);
bool ignored;
if (Value.convertToInteger(Result, llvm::APFloat::rmTowardZero, &ignored)
    & APFloat::opInvalidOp)
  return HandleOverflow(Info, E, Value, DestType);
return true;
2536}

2538/// Get rounding mode used for evaluation of the specified expression.
2539/// \param[out] DynamicRM Is set to true is the requested rounding mode is
2540///                       dynamic.
2541/// If rounding mode is unknown at compile time, still try to evaluate the
2542/// expression. If the result is exact, it does not depend on rounding mode.
2543/// So return "tonearest" mode instead of "dynamic".
2544static llvm::RoundingMode getActiveRoundingMode(EvalInfo &Info, const Expr *E,
                                              bool &DynamicRM) {
llvm::RoundingMode RM =
    E->getFPFeaturesInEffect(Info.Ctx.getLangOpts()).getRoundingMode();
DynamicRM = (RM == llvm::RoundingMode::Dynamic);
if (DynamicRM)
  RM = llvm::RoundingMode::NearestTiesToEven;
return RM;
2552}

2554/// Check if the given evaluation result is allowed for constant evaluation.
2555static bool checkFloatingPointResult(EvalInfo &Info, const Expr *E,
                                   APFloat::opStatus St) {
// In a constant context, assume that any dynamic rounding mode or FP
// exception state matches the default floating-point environment.
if (Info.InConstantContext)
  return true;

FPOptions FPO = E->getFPFeaturesInEffect(Info.Ctx.getLangOpts());
if ((St & APFloat::opInexact) &&
    FPO.getRoundingMode() == llvm::RoundingMode::Dynamic) {
  // Inexact result means that it depends on rounding mode. If the requested
  // mode is dynamic, the evaluation cannot be made in compile time.
  Info.FFDiag(E, diag::note_constexpr_dynamic_rounding);
  return false;
}

if ((St != APFloat::opOK) &&
    (FPO.getRoundingMode() == llvm::RoundingMode::Dynamic ||
     FPO.getFPExceptionMode() != LangOptions::FPE_Ignore ||
     FPO.getAllowFEnvAccess())) {
  Info.FFDiag(E, diag::note_constexpr_float_arithmetic_strict);
  return false;
}

if ((St & APFloat::opStatus::opInvalidOp) &&
    FPO.getFPExceptionMode() != LangOptions::FPE_Ignore) {
  // There is no usefully definable result.
  Info.FFDiag(E);
  return false;
}

// FIXME: if:
// - evaluation triggered other FP exception, and
// - exception mode is not "ignore", and
// - the expression being evaluated is not a part of global variable
//   initializer,
// the evaluation probably need to be rejected.
return true;
2593}

2595static bool HandleFloatToFloatCast(EvalInfo &Info, const Expr *E,
                                 QualType SrcType, QualType DestType,
                                 APFloat &Result) {
assert(isa<CastExpr>(E) || isa<CompoundAssignOperator>(E))((void)0);
bool DynamicRM;
llvm::RoundingMode RM = getActiveRoundingMode(Info, E, DynamicRM);
APFloat::opStatus St;
APFloat Value = Result;
bool ignored;
St = Result.convert(Info.Ctx.getFloatTypeSemantics(DestType), RM, &ignored);
return checkFloatingPointResult(Info, E, St);
2606}

2608static APSInt HandleIntToIntCast(EvalInfo &Info, const Expr *E,
                               QualType DestType, QualType SrcType,
                               const APSInt &Value) {
unsigned DestWidth = Info.Ctx.getIntWidth(DestType);
// Figure out if this is a truncate, extend or noop cast.
// If the input is signed, do a sign extend, noop, or truncate.
APSInt Result = Value.extOrTrunc(DestWidth);
Result.setIsUnsigned(DestType->isUnsignedIntegerOrEnumerationType());
if (DestType->isBooleanType())
  Result = Value.getBoolValue();
return Result;
2619}

2621static bool HandleIntToFloatCast(EvalInfo &Info, const Expr *E,
                               const FPOptions FPO,
                               QualType SrcType, const APSInt &Value,
                               QualType DestType, APFloat &Result) {
Result = APFloat(Info.Ctx.getFloatTypeSemantics(DestType), 1);
APFloat::opStatus St = Result.convertFromAPInt(Value, Value.isSigned(),
     APFloat::rmNearestTiesToEven);
if (!Info.InConstantContext && St != llvm::APFloatBase::opOK &&
    FPO.isFPConstrained()) {
  Info.FFDiag(E, diag::note_constexpr_float_arithmetic_strict);
  return false;
}
return true;
2634}

2636static bool truncateBitfieldValue(EvalInfo &Info, const Expr *E,
                                APValue &Value, const FieldDecl *FD) {
assert(FD->isBitField() && "truncateBitfieldValue on non-bitfield")((void)0);

if (!Value.isInt()) {
  // Trying to store a pointer-cast-to-integer into a bitfield.
  // FIXME: In this case, we should provide the diagnostic for casting
  // a pointer to an integer.
  assert(Value.isLValue() && "integral value neither int nor lvalue?")((void)0);
  Info.FFDiag(E);
  return false;
}

APSInt &Int = Value.getInt();
unsigned OldBitWidth = Int.getBitWidth();
unsigned NewBitWidth = FD->getBitWidthValue(Info.Ctx);
if (NewBitWidth < OldBitWidth)
  Int = Int.trunc(NewBitWidth).extend(OldBitWidth);
return true;
2655}

2657static bool EvalAndBitcastToAPInt(EvalInfo &Info, const Expr *E,
                                llvm::APInt &Res) {
APValue SVal;
if (!Evaluate(SVal, Info, E))
  return false;
if (SVal.isInt()) {
  Res = SVal.getInt();
  return true;
}
if (SVal.isFloat()) {
  Res = SVal.getFloat().bitcastToAPInt();
  return true;
}
if (SVal.isVector()) {
  QualType VecTy = E->getType();
  unsigned VecSize = Info.Ctx.getTypeSize(VecTy);
  QualType EltTy = VecTy->castAs<VectorType>()->getElementType();
  unsigned EltSize = Info.Ctx.getTypeSize(EltTy);
  bool BigEndian = Info.Ctx.getTargetInfo().isBigEndian();
  Res = llvm::APInt::getNullValue(VecSize);
  for (unsigned i = 0; i < SVal.getVectorLength(); i++) {
    APValue &Elt = SVal.getVectorElt(i);
    llvm::APInt EltAsInt;
    if (Elt.isInt()) {
      EltAsInt = Elt.getInt();
    } else if (Elt.isFloat()) {
      EltAsInt = Elt.getFloat().bitcastToAPInt();
    } else {
      // Don't try to handle vectors of anything other than int or float
      // (not sure if it's possible to hit this case).
      Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
      return false;
    }
    unsigned BaseEltSize = EltAsInt.getBitWidth();
    if (BigEndian)
      Res |= EltAsInt.zextOrTrunc(VecSize).rotr(i*EltSize+BaseEltSize);
    else
      Res |= EltAsInt.zextOrTrunc(VecSize).rotl(i*EltSize);
  }
  return true;
}
// Give up if the input isn't an int, float, or vector.  For example, we
// reject "(v4i16)(intptr_t)&a".
Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
return false;
2702}

2704/// Perform the given integer operation, which is known to need at most BitWidth
2705/// bits, and check for overflow in the original type (if that type was not an
2706/// unsigned type).
2707template<typename Operation>
2708static bool CheckedIntArithmetic(EvalInfo &Info, const Expr *E,
                               const APSInt &LHS, const APSInt &RHS,
                               unsigned BitWidth, Operation Op,
                               APSInt &Result) {
if (LHS.isUnsigned()) {
  Result = Op(LHS, RHS);
  return true;
}

APSInt Value(Op(LHS.extend(BitWidth), RHS.extend(BitWidth)), false);
Result = Value.trunc(LHS.getBitWidth());
if (Result.extend(BitWidth) != Value) {
  if (Info.checkingForUndefinedBehavior())
    Info.Ctx.getDiagnostics().Report(E->getExprLoc(),
                                     diag::warn_integer_constant_overflow)
        << toString(Result, 10) << E->getType();
  return HandleOverflow(Info, E, Value, E->getType());
}
return true;
2727}

2729/// Perform the given binary integer operation.
2730static bool handleIntIntBinOp(EvalInfo &Info, const Expr *E, const APSInt &LHS,
                            BinaryOperatorKind Opcode, APSInt RHS,
                            APSInt &Result) {
switch (Opcode) {
default:
  Info.FFDiag(E);
  return false;
case BO_Mul:
  return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() * 2,
                              std::multiplies<APSInt>(), Result);
case BO_Add:
  return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() + 1,
                              std::plus<APSInt>(), Result);
case BO_Sub:
  return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() + 1,
                              std::minus<APSInt>(), Result);
case BO_And: Result = LHS & RHS; return true;
case BO_Xor: Result = LHS ^ RHS; return true;
case BO_Or:  Result = LHS | RHS; return true;
case BO_Div:
case BO_Rem:
  if (RHS == 0) {
    Info.FFDiag(E, diag::note_expr_divide_by_zero);
    return false;
  }
  Result = (Opcode == BO_Rem ? LHS % RHS : LHS / RHS);
  // Check for overflow case: INT_MIN / -1 or INT_MIN % -1. APSInt supports
  // this operation and gives the two's complement result.
  if (RHS.isNegative() && RHS.isAllOnesValue() &&
      LHS.isSigned() && LHS.isMinSignedValue())
    return HandleOverflow(Info, E, -LHS.extend(LHS.getBitWidth() + 1),
                          E->getType());
  return true;
case BO_Shl: {
  if (Info.getLangOpts().OpenCL)
    // OpenCL 6.3j: shift values are effectively % word size of LHS.
    RHS &= APSInt(llvm::APInt(RHS.getBitWidth(),
                  static_cast<uint64_t>(LHS.getBitWidth() - 1)),
                  RHS.isUnsigned());
  else if (RHS.isSigned() && RHS.isNegative()) {
    // During constant-folding, a negative shift is an opposite shift. Such
    // a shift is not a constant expression.
    Info.CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
    RHS = -RHS;
    goto shift_right;
  }
shift_left:
  // C++11 [expr.shift]p1: Shift width must be less than the bit width of
  // the shifted type.
  unsigned SA = (unsigned) RHS.getLimitedValue(LHS.getBitWidth()-1);
  if (SA != RHS) {
    Info.CCEDiag(E, diag::note_constexpr_large_shift)
      << RHS << E->getType() << LHS.getBitWidth();
  } else if (LHS.isSigned() && !Info.getLangOpts().CPlusPlus20) {
    // C++11 [expr.shift]p2: A signed left shift must have a non-negative
    // operand, and must not overflow the corresponding unsigned type.
    // C++2a [expr.shift]p2: E1 << E2 is the unique value congruent to
    // E1 x 2^E2 module 2^N.
    if (LHS.isNegative())
      Info.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << LHS;
    else if (LHS.countLeadingZeros() < SA)
      Info.CCEDiag(E, diag::note_constexpr_lshift_discards);
  }
  Result = LHS << SA;
  return true;
}
case BO_Shr: {
  if (Info.getLangOpts().OpenCL)
    // OpenCL 6.3j: shift values are effectively % word size of LHS.
    RHS &= APSInt(llvm::APInt(RHS.getBitWidth(),
                  static_cast<uint64_t>(LHS.getBitWidth() - 1)),
                  RHS.isUnsigned());
  else if (RHS.isSigned() && RHS.isNegative()) {
    // During constant-folding, a negative shift is an opposite shift. Such a
    // shift is not a constant expression.
    Info.CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
    RHS = -RHS;
    goto shift_left;
  }
shift_right:
  // C++11 [expr.shift]p1: Shift width must be less than the bit width of the
  // shifted type.
  unsigned SA = (unsigned) RHS.getLimitedValue(LHS.getBitWidth()-1);
  if (SA != RHS)
    Info.CCEDiag(E, diag::note_constexpr_large_shift)
      << RHS << E->getType() << LHS.getBitWidth();
  Result = LHS >> SA;
  return true;
}

case BO_LT: Result = LHS < RHS; return true;
case BO_GT: Result = LHS > RHS; return true;
case BO_LE: Result = LHS <= RHS; return true;
case BO_GE: Result = LHS >= RHS; return true;
case BO_EQ: Result = LHS == RHS; return true;
case BO_NE: Result = LHS != RHS; return true;
case BO_Cmp:
  llvm_unreachable("BO_Cmp should be handled elsewhere")__builtin_unreachable();
}
2829}

2831/// Perform the given binary floating-point operation, in-place, on LHS.
2832static bool handleFloatFloatBinOp(EvalInfo &Info, const BinaryOperator *E,
                                APFloat &LHS, BinaryOperatorKind Opcode,
                                const APFloat &RHS) {
bool DynamicRM;
llvm::RoundingMode RM = getActiveRoundingMode(Info, E, DynamicRM);
APFloat::opStatus St;
switch (Opcode) {
default:
  Info.FFDiag(E);
  return false;
case BO_Mul:
  St = LHS.multiply(RHS, RM);
  break;
case BO_Add:
  St = LHS.add(RHS, RM);
  break;
case BO_Sub:
  St = LHS.subtract(RHS, RM);
  break;
case BO_Div:
  // [expr.mul]p4:
  //   If the second operand of / or % is zero the behavior is undefined.
  if (RHS.isZero())
    Info.CCEDiag(E, diag::note_expr_divide_by_zero);
  St = LHS.divide(RHS, RM);
  break;
}

// [expr.pre]p4:
//   If during the evaluation of an expression, the result is not
//   mathematically defined [...], the behavior is undefined.
// FIXME: C++ rules require us to not conform to IEEE 754 here.
if (LHS.isNaN()) {
  Info.CCEDiag(E, diag::note_constexpr_float_arithmetic) << LHS.isNaN();
  return Info.noteUndefinedBehavior();
}

return checkFloatingPointResult(Info, E, St);
2870}

2872static bool handleLogicalOpForVector(const APInt &LHSValue,
                                   BinaryOperatorKind Opcode,
                                   const APInt &RHSValue, APInt &Result) {
bool LHS = (LHSValue != 0);
bool RHS = (RHSValue != 0);

if (Opcode == BO_LAnd)
  Result = LHS && RHS;
else
  Result = LHS || RHS;
return true;
2883}
2884static bool handleLogicalOpForVector(const APFloat &LHSValue,
                                   BinaryOperatorKind Opcode,
                                   const APFloat &RHSValue, APInt &Result) {
bool LHS = !LHSValue.isZero();
bool RHS = !RHSValue.isZero();

if (Opcode == BO_LAnd)
  Result = LHS && RHS;
else
  Result = LHS || RHS;
return true;
2895}

2897static bool handleLogicalOpForVector(const APValue &LHSValue,
                                   BinaryOperatorKind Opcode,
                                   const APValue &RHSValue, APInt &Result) {
// The result is always an int type, however operands match the first.
if (LHSValue.getKind() == APValue::Int)
  return handleLogicalOpForVector(LHSValue.getInt(), Opcode,
                                  RHSValue.getInt(), Result);
assert(LHSValue.getKind() == APValue::Float && "Should be no other options")((void)0);
return handleLogicalOpForVector(LHSValue.getFloat(), Opcode,
                                RHSValue.getFloat(), Result);
2907}

2909template <typename APTy>
2910static bool
2911handleCompareOpForVectorHelper(const APTy &LHSValue, BinaryOperatorKind Opcode,
                             const APTy &RHSValue, APInt &Result) {
switch (Opcode) {
default:
  llvm_unreachable("unsupported binary operator")__builtin_unreachable();
case BO_EQ:
  Result = (LHSValue == RHSValue);
  break;
case BO_NE:
  Result = (LHSValue != RHSValue);
  break;
case BO_LT:
  Result = (LHSValue < RHSValue);
  break;
case BO_GT:
  Result = (LHSValue > RHSValue);
  break;
case BO_LE:
  Result = (LHSValue <= RHSValue);
  break;
case BO_GE:
  Result = (LHSValue >= RHSValue);
  break;
}

return true;
2937}

2939static bool handleCompareOpForVector(const APValue &LHSValue,
                                   BinaryOperatorKind Opcode,
                                   const APValue &RHSValue, APInt &Result) {
// The result is always an int type, however operands match the first.
if (LHSValue.getKind() == APValue::Int)
  return handleCompareOpForVectorHelper(LHSValue.getInt(), Opcode,
                                        RHSValue.getInt(), Result);
assert(LHSValue.getKind() == APValue::Float && "Should be no other options")((void)0);
return handleCompareOpForVectorHelper(LHSValue.getFloat(), Opcode,
                                      RHSValue.getFloat(), Result);
2949}

2951// Perform binary operations for vector types, in place on the LHS.
2952static bool handleVectorVectorBinOp(EvalInfo &Info, const BinaryOperator *E,
                                  BinaryOperatorKind Opcode,
                                  APValue &LHSValue,
                                  const APValue &RHSValue) {
assert(Opcode != BO_PtrMemD && Opcode != BO_PtrMemI &&((void)0)
       "Operation not supported on vector types")((void)0);

const auto *VT = E->getType()->castAs<VectorType>();
unsigned NumElements = VT->getNumElements();
QualType EltTy = VT->getElementType();

// In the cases (typically C as I've observed) where we aren't evaluating
// constexpr but are checking for cases where the LHS isn't yet evaluatable,
// just give up.
if (!LHSValue.isVector()) {
  assert(LHSValue.isLValue() &&((void)0)
         "A vector result that isn't a vector OR uncalculated LValue")((void)0);
  Info.FFDiag(E);
  return false;
}

assert(LHSValue.getVectorLength() == NumElements &&((void)0)
       RHSValue.getVectorLength() == NumElements && "Different vector sizes")((void)0);

SmallVector<APValue, 4> ResultElements;

for (unsigned EltNum = 0; EltNum < NumElements; ++EltNum) {
  APValue LHSElt = LHSValue.getVectorElt(EltNum);
  APValue RHSElt = RHSValue.getVectorElt(EltNum);

  if (EltTy->isIntegerType()) {
    APSInt EltResult{Info.Ctx.getIntWidth(EltTy),
                     EltTy->isUnsignedIntegerType()};
    bool Success = true;

    if (BinaryOperator::isLogicalOp(Opcode))
      Success = handleLogicalOpForVector(LHSElt, Opcode, RHSElt, EltResult);
    else if (BinaryOperator::isComparisonOp(Opcode))
      Success = handleCompareOpForVector(LHSElt, Opcode, RHSElt, EltResult);
    else
      Success = handleIntIntBinOp(Info, E, LHSElt.getInt(), Opcode,
                                  RHSElt.getInt(), EltResult);

    if (!Success) {
      Info.FFDiag(E);
      return false;
    }
    ResultElements.emplace_back(EltResult);

  } else if (EltTy->isFloatingType()) {
    assert(LHSElt.getKind() == APValue::Float &&((void)0)
           RHSElt.getKind() == APValue::Float &&((void)0)
           "Mismatched LHS/RHS/Result Type")((void)0);
    APFloat LHSFloat = LHSElt.getFloat();

    if (!handleFloatFloatBinOp(Info, E, LHSFloat, Opcode,
                               RHSElt.getFloat())) {
      Info.FFDiag(E);
      return false;
    }

    ResultElements.emplace_back(LHSFloat);
  }
}

LHSValue = APValue(ResultElements.data(), ResultElements.size());
return true;
3019}

3021/// Cast an lvalue referring to a base subobject to a derived class, by
3022/// truncating the lvalue's path to the given length.
3023static bool CastToDerivedClass(EvalInfo &Info, const Expr *E, LValue &Result,
                             const RecordDecl *TruncatedType,
                             unsigned TruncatedElements) {
SubobjectDesignator &D = Result.Designator;

// Check we actually point to a derived class object.
if (TruncatedElements == D.Entries.size())
  return true;
assert(TruncatedElements >= D.MostDerivedPathLength &&((void)0)
       "not casting to a derived class")((void)0);
if (!Result.checkSubobject(Info, E, CSK_Derived))
  return false;

// Truncate the path to the subobject, and remove any derived-to-base offsets.
const RecordDecl *RD = TruncatedType;
for (unsigned I = TruncatedElements, N = D.Entries.size(); I != N; ++I) {
  if (RD->isInvalidDecl()) return false;
  const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
  const CXXRecordDecl *Base = getAsBaseClass(D.Entries[I]);
  if (isVirtualBaseClass(D.Entries[I]))
    Result.Offset -= Layout.getVBaseClassOffset(Base);
  else
    Result.Offset -= Layout.getBaseClassOffset(Base);
  RD = Base;
}
D.Entries.resize(TruncatedElements);
return true;
3050}

3052static bool HandleLValueDirectBase(EvalInfo &Info, const Expr *E, LValue &Obj,
                                 const CXXRecordDecl *Derived,
                                 const CXXRecordDecl *Base,
                                 const ASTRecordLayout *RL = nullptr) {
if (!RL) {
  if (Derived->isInvalidDecl()) return false;
  RL = &Info.Ctx.getASTRecordLayout(Derived);
}

Obj.getLValueOffset() += RL->getBaseClassOffset(Base);
Obj.addDecl(Info, E, Base, /*Virtual*/ false);
return true;
3064}

3066static bool HandleLValueBase(EvalInfo &Info, const Expr *E, LValue &Obj,
                           const CXXRecordDecl *DerivedDecl,
                           const CXXBaseSpecifier *Base) {
const CXXRecordDecl *BaseDecl = Base->getType()->getAsCXXRecordDecl();

if (!Base->isVirtual())
  return HandleLValueDirectBase(Info, E, Obj, DerivedDecl, BaseDecl);

SubobjectDesignator &D = Obj.Designator;
if (D.Invalid)
  return false;

// Extract most-derived object and corresponding type.
DerivedDecl = D.MostDerivedType->getAsCXXRecordDecl();
if (!CastToDerivedClass(Info, E, Obj, DerivedDecl, D.MostDerivedPathLength))
  return false;

// Find the virtual base class.
if (DerivedDecl->isInvalidDecl()) return false;
const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(DerivedDecl);
Obj.getLValueOffset() += Layout.getVBaseClassOffset(BaseDecl);
Obj.addDecl(Info, E, BaseDecl, /*Virtual*/ true);
return true;
3089}

3091static bool HandleLValueBasePath(EvalInfo &Info, const CastExpr *E,
                               QualType Type, LValue &Result) {
for (CastExpr::path_const_iterator PathI = E->path_begin(),
                                   PathE = E->path_end();
     PathI != PathE; ++PathI) {
  if (!HandleLValueBase(Info, E, Result, Type->getAsCXXRecordDecl(),
                        *PathI))
    return false;
  Type = (*PathI)->getType();
}
return true;
3102}

3104/// Cast an lvalue referring to a derived class to a known base subobject.
3105static bool CastToBaseClass(EvalInfo &Info, const Expr *E, LValue &Result,
                          const CXXRecordDecl *DerivedRD,
                          const CXXRecordDecl *BaseRD) {
CXXBasePaths Paths(/*FindAmbiguities=*/false,
                   /*RecordPaths=*/true, /*DetectVirtual=*/false);
if (!DerivedRD->isDerivedFrom(BaseRD, Paths))
  llvm_unreachable("Class must be derived from the passed in base class!")__builtin_unreachable();

for (CXXBasePathElement &Elem : Paths.front())
  if (!HandleLValueBase(Info, E, Result, Elem.Class, Elem.Base))
    return false;
return true;
3117}

3119/// Update LVal to refer to the given field, which must be a member of the type
3120/// currently described by LVal.
3121static bool HandleLValueMember(EvalInfo &Info, const Expr *E, LValue &LVal,
                             const FieldDecl *FD,
                             const ASTRecordLayout *RL = nullptr) {
if (!RL) {
  if (FD->getParent()->isInvalidDecl()) return false;
  RL = &Info.Ctx.getASTRecordLayout(FD->getParent());
}

unsigned I = FD->getFieldIndex();
LVal.adjustOffset(Info.Ctx.toCharUnitsFromBits(RL->getFieldOffset(I)));
LVal.addDecl(Info, E, FD);
return true;
3133}

3135/// Update LVal to refer to the given indirect field.
3136static bool HandleLValueIndirectMember(EvalInfo &Info, const Expr *E,
                                     LValue &LVal,
                                     const IndirectFieldDecl *IFD) {
for (const auto *C : IFD->chain())
  if (!HandleLValueMember(Info, E, LVal, cast<FieldDecl>(C)))
    return false;
return true;
3143}

3145/// Get the size of the given type in char units.
3146static bool HandleSizeof(EvalInfo &Info, SourceLocation Loc,
                       QualType Type, CharUnits &Size) {
// sizeof(void), __alignof__(void), sizeof(function) = 1 as a gcc
// extension.
if (Type->isVoidType() || Type->isFunctionType()) {
  Size = CharUnits::One();
  return true;
}

if (Type->isDependentType()) {
  Info.FFDiag(Loc);
  return false;
}

if (!Type->isConstantSizeType()) {
  // sizeof(vla) is not a constantexpr: C99 6.5.3.4p2.
  // FIXME: Better diagnostic.
  Info.FFDiag(Loc);
  return false;
}

Size = Info.Ctx.getTypeSizeInChars(Type);
return true;
3169}

3171/// Update a pointer value to model pointer arithmetic.
3172/// \param Info - Information about the ongoing evaluation.
3173/// \param E - The expression being evaluated, for diagnostic purposes.
3174/// \param LVal - The pointer value to be updated.
3175/// \param EltTy - The pointee type represented by LVal.
3176/// \param Adjustment - The adjustment, in objects of type EltTy, to add.
3177static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
                                      LValue &LVal, QualType EltTy,
                                      APSInt Adjustment) {
CharUnits SizeOfPointee;
if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfPointee))
  return false;

LVal.adjustOffsetAndIndex(Info, E, Adjustment, SizeOfPointee);
return true;
3186}

3188static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
                                      LValue &LVal, QualType EltTy,
                                      int64_t Adjustment) {
return HandleLValueArrayAdjustment(Info, E, LVal, EltTy,
                                   APSInt::get(Adjustment));
3193}

3195/// Update an lvalue to refer to a component of a complex number.
3196/// \param Info - Information about the ongoing evaluation.
3197/// \param LVal - The lvalue to be updated.
3198/// \param EltTy - The complex number's component type.
3199/// \param Imag - False for the real component, true for the imaginary.
3200static bool HandleLValueComplexElement(EvalInfo &Info, const Expr *E,
                                     LValue &LVal, QualType EltTy,
                                     bool Imag) {
if (Imag) {
  CharUnits SizeOfComponent;
  if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfComponent))
    return false;
  LVal.Offset += SizeOfComponent;
}
LVal.addComplex(Info, E, EltTy, Imag);
return true;
3211}

3213/// Try to evaluate the initializer for a variable declaration.
3214///
3215/// \param Info   Information about the ongoing evaluation.
3216/// \param E      An expression to be used when printing diagnostics.
3217/// \param VD     The variable whose initializer should be obtained.
3218/// \param Version The version of the variable within the frame.
3219/// \param Frame  The frame in which the variable was created. Must be null
3220///               if this variable is not local to the evaluation.
3221/// \param Result Filled in with a pointer to the value of the variable.
3222static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E,
                              const VarDecl *VD, CallStackFrame *Frame,
                              unsigned Version, APValue *&Result) {
APValue::LValueBase Base(VD, Frame ? Frame->Index : 0, Version);

// If this is a local variable, dig out its value.
if (Frame) {
  Result = Frame->getTemporary(VD, Version);
  if (Result)
    return true;

  if (!isa<ParmVarDecl>(VD)) {
    // Assume variables referenced within a lambda's call operator that were
    // not declared within the call operator are captures and during checking
    // of a potential constant expression, assume they are unknown constant
    // expressions.
    assert(isLambdaCallOperator(Frame->Callee) &&((void)0)
           (VD->getDeclContext() != Frame->Callee || VD->isInitCapture()) &&((void)0)
           "missing value for local variable")((void)0);
    if (Info.checkingPotentialConstantExpression())
      return false;
    // FIXME: This diagnostic is bogus; we do support captures. Is this code
    // still reachable at all?
    Info.FFDiag(E->getBeginLoc(),
                diag::note_unimplemented_constexpr_lambda_feature_ast)
        << "captures not currently allowed";
    return false;
  }
}

// If we're currently evaluating the initializer of this declaration, use that
// in-flight value.
if (Info.EvaluatingDecl == Base) {
  Result = Info.EvaluatingDeclValue;
  return true;
}

if (isa<ParmVarDecl>(VD)) {
  // Assume parameters of a potential constant expression are usable in
  // constant expressions.
  if (!Info.checkingPotentialConstantExpression() ||
      !Info.CurrentCall->Callee ||
      !Info.CurrentCall->Callee->Equals(VD->getDeclContext())) {
    if (Info.getLangOpts().CPlusPlus11) {
      Info.FFDiag(E, diag::note_constexpr_function_param_value_unknown)
          << VD;
      NoteLValueLocation(Info, Base);
    } else {
      Info.FFDiag(E);
    }
  }
  return false;
}

// Dig out the initializer, and use the declaration which it's attached to.
// FIXME: We should eventually check whether the variable has a reachable
// initializing declaration.
const Expr *Init = VD->getAnyInitializer(VD);
if (!Init) {
  // Don't diagnose during potential constant expression checking; an
  // initializer might be added later.
  if (!Info.checkingPotentialConstantExpression()) {
    Info.FFDiag(E, diag::note_constexpr_var_init_unknown, 1)
      << VD;
    NoteLValueLocation(Info, Base);
  }
  return false;
}

if (Init->isValueDependent()) {
  // The DeclRefExpr is not value-dependent, but the variable it refers to
  // has a value-dependent initializer. This should only happen in
  // constant-folding cases, where the variable is not actually of a suitable
  // type for use in a constant expression (otherwise the DeclRefExpr would
  // have been value-dependent too), so diagnose that.
  assert(!VD->mightBeUsableInConstantExpressions(Info.Ctx))((void)0);
  if (!Info.checkingPotentialConstantExpression()) {
    Info.FFDiag(E, Info.getLangOpts().CPlusPlus11
                       ? diag::note_constexpr_ltor_non_constexpr
                       : diag::note_constexpr_ltor_non_integral, 1)
        << VD << VD->getType();
    NoteLValueLocation(Info, Base);
  }
  return false;
}

// Check that we can fold the initializer. In C++, we will have already done
// this in the cases where it matters for conformance.
if (!VD->evaluateValue()) {
  Info.FFDiag(E, diag::note_constexpr_var_init_non_constant, 1) << VD;
  NoteLValueLocation(Info, Base);
  return false;
}

// Check that the variable is actually usable in constant expressions. For a
// const integral variable or a reference, we might have a non-constant
// initializer that we can nonetheless evaluate the initializer for. Such
// variables are not usable in constant expressions. In C++98, the
// initializer also syntactically needs to be an ICE.
//
// FIXME: We don't diagnose cases that aren't potentially usable in constant
// expressions here; doing so would regress diagnostics for things like
// reading from a volatile constexpr variable.
if ((Info.getLangOpts().CPlusPlus && !VD->hasConstantInitialization() &&
     VD->mightBeUsableInConstantExpressions(Info.Ctx)) ||
    ((Info.getLangOpts().CPlusPlus || Info.getLangOpts().OpenCL) &&
     !Info.getLangOpts().CPlusPlus11 && !VD->hasICEInitializer(Info.Ctx))) {
  Info.CCEDiag(E, diag::note_constexpr_var_init_non_constant, 1) << VD;
  NoteLValueLocation(Info, Base);
}

// Never use the initializer of a weak variable, not even for constant
// folding. We can't be sure that this is the definition that will be used.
if (VD->isWeak()) {
  Info.FFDiag(E, diag::note_constexpr_var_init_weak) << VD;
  NoteLValueLocation(Info, Base);
  return false;
}

Result = VD->getEvaluatedValue();
return true;
3343}

3345/// Get the base index of the given base class within an APValue representing
3346/// the given derived class.
3347static unsigned getBaseIndex(const CXXRecordDecl *Derived,
                           const CXXRecordDecl *Base) {
Base = Base->getCanonicalDecl();
unsigned Index = 0;
for (CXXRecordDecl::base_class_const_iterator I = Derived->bases_begin(),
       E = Derived->bases_end(); I != E; ++I, ++Index) {
  if (I->getType()->getAsCXXRecordDecl()->getCanonicalDecl() == Base)
    return Index;
}

llvm_unreachable("base class missing from derived class's bases list")__builtin_unreachable();
3358}

3360/// Extract the value of a character from a string literal.
3361static APSInt extractStringLiteralCharacter(EvalInfo &Info, const Expr *Lit,
                                          uint64_t Index) {
assert(!isa<SourceLocExpr>(Lit) &&((void)0)
       "SourceLocExpr should have already been converted to a StringLiteral")((void)0);

// FIXME: Support MakeStringConstant
if (const auto *ObjCEnc = dyn_cast<ObjCEncodeExpr>(Lit)) {
  std::string Str;
  Info.Ctx.getObjCEncodingForType(ObjCEnc->getEncodedType(), Str);
  assert(Index <= Str.size() && "Index too large")((void)0);
  return APSInt::getUnsigned(Str.c_str()[Index]);
}

if (auto PE = dyn_cast<PredefinedExpr>(Lit))
  Lit = PE->getFunctionName();
const StringLiteral *S = cast<StringLiteral>(Lit);
const ConstantArrayType *CAT =
    Info.Ctx.getAsConstantArrayType(S->getType());
assert(CAT && "string literal isn't an array")((void)0);
QualType CharType = CAT->getElementType();
assert(CharType->isIntegerType() && "unexpected character type")((void)0);

APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
             CharType->isUnsignedIntegerType());
if (Index < S->getLength())
  Value = S->getCodeUnit(Index);
return Value;
3388}

3390// Expand a string literal into an array of characters.
3391//
3392// FIXME: This is inefficient; we should probably introduce something similar
3393// to the LLVM ConstantDataArray to make this cheaper.
3394static void expandStringLiteral(EvalInfo &Info, const StringLiteral *S,
                              APValue &Result,
                              QualType AllocType = QualType()) {
const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(
    AllocType.isNull() ? S->getType() : AllocType);
assert(CAT && "string literal isn't an array")((void)0);
QualType CharType = CAT->getElementType();
assert(CharType->isIntegerType() && "unexpected character type")((void)0);

unsigned Elts = CAT->getSize().getZExtValue();
Result = APValue(APValue::UninitArray(),
                 std::min(S->getLength(), Elts), Elts);
APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
             CharType->isUnsignedIntegerType());
if (Result.hasArrayFiller())
  Result.getArrayFiller() = APValue(Value);
for (unsigned I = 0, N = Result.getArrayInitializedElts(); I != N; ++I) {
  Value = S->getCodeUnit(I);
  Result.getArrayInitializedElt(I) = APValue(Value);
}
3414}

3416// Expand an array so that it has more than Index filled elements.
3417static void expandArray(APValue &Array, unsigned Index) {
unsigned Size = Array.getArraySize();
assert(Index < Size)((void)0);

// Always at least double the number of elements for which we store a value.
unsigned OldElts = Array.getArrayInitializedElts();
unsigned NewElts = std::max(Index+1, OldElts * 2);
NewElts = std::min(Size, std::max(NewElts, 8u));

// Copy the data across.
APValue NewValue(APValue::UninitArray(), NewElts, Size);
for (unsigned I = 0; I != OldElts; ++I)
  NewValue.getArrayInitializedElt(I).swap(Array.getArrayInitializedElt(I));
for (unsigned I = OldElts; I != NewElts; ++I)
  NewValue.getArrayInitializedElt(I) = Array.getArrayFiller();
if (NewValue.hasArrayFiller())
  NewValue.getArrayFiller() = Array.getArrayFiller();
Array.swap(NewValue);
3435}

3437/// Determine whether a type would actually be read by an lvalue-to-rvalue
3438/// conversion. If it's of class type, we may assume that the copy operation
3439/// is trivial. Note that this is never true for a union type with fields
3440/// (because the copy always "reads" the active member) and always true for
3441/// a non-class type.
3442static bool isReadByLvalueToRvalueConversion(const CXXRecordDecl *RD);
3443static bool isReadByLvalueToRvalueConversion(QualType T) {
CXXRecordDecl *RD = T->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
return !RD || isReadByLvalueToRvalueConversion(RD);
3446}
3447static bool isReadByLvalueToRvalueConversion(const CXXRecordDecl *RD) {
// FIXME: A trivial copy of a union copies the object representation, even if
// the union is empty.
if (RD->isUnion())
38
←
Calling 'TagDecl::isUnion'→
41
←
Returning from 'TagDecl::isUnion'→
42
←
Taking true branch→
  return !RD->field_empty();
43
←
Calling 'RecordDecl::field_empty'→
52
←
Returning from 'RecordDecl::field_empty'→
53
←
Returning the value 1, which participates in a condition later→
if (RD->isEmpty())
  return false;

for (auto *Field : RD->fields())
  if (!Field->isUnnamedBitfield() &&
      isReadByLvalueToRvalueConversion(Field->getType()))
    return true;

for (auto &BaseSpec : RD->bases())
  if (isReadByLvalueToRvalueConversion(BaseSpec.getType()))
    return true;

return false;
3465}

3467/// Diagnose an attempt to read from any unreadable field within the specified
3468/// type, which might be a class type.
3469static bool diagnoseMutableFields(EvalInfo &Info, const Expr *E, AccessKinds AK,
                                QualType T) {
CXXRecordDecl *RD = T->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
if (!RD)
  return false;

if (!RD->hasMutableFields())
  return false;

for (auto *Field : RD->fields()) {
  // If we're actually going to read this field in some way, then it can't
  // be mutable. If we're in a union, then assigning to a mutable field
  // (even an empty one) can change the active member, so that's not OK.
  // FIXME: Add core issue number for the union case.
  if (Field->isMutable() &&
      (RD->isUnion() || isReadByLvalueToRvalueConversion(Field->getType()))) {
    Info.FFDiag(E, diag::note_constexpr_access_mutable, 1) << AK << Field;
    Info.Note(Field->getLocation(), diag::note_declared_at);
    return true;
  }

  if (diagnoseMutableFields(Info, E, AK, Field->getType()))
    return true;
}

for (auto &BaseSpec : RD->bases())
  if (diagnoseMutableFields(Info, E, AK, BaseSpec.getType()))
    return true;

// All mutable fields were empty, and thus not actually read.
return false;
3500}

3502static bool lifetimeStartedInEvaluation(EvalInfo &Info,
                                      APValue::LValueBase Base,
                                      bool MutableSubobject = false) {
// A temporary or transient heap allocation we created.
if (Base.getCallIndex() || Base.is<DynamicAllocLValue>())
  return true;

switch (Info.IsEvaluatingDecl) {
case EvalInfo::EvaluatingDeclKind::None:
  return false;

case EvalInfo::EvaluatingDeclKind::Ctor:
  // The variable whose initializer we're evaluating.
  if (Info.EvaluatingDecl == Base)
    return true;

  // A temporary lifetime-extended by the variable whose initializer we're
  // evaluating.
  if (auto *BaseE = Base.dyn_cast<const Expr *>())
    if (auto *BaseMTE = dyn_cast<MaterializeTemporaryExpr>(BaseE))
      return Info.EvaluatingDecl == BaseMTE->getExtendingDecl();
  return false;

case EvalInfo::EvaluatingDeclKind::Dtor:
  // C++2a [expr.const]p6:
  //   [during constant destruction] the lifetime of a and its non-mutable
  //   subobjects (but not its mutable subobjects) [are] considered to start
  //   within e.
  if (MutableSubobject || Base != Info.EvaluatingDecl)
    return false;
  // FIXME: We can meaningfully extend this to cover non-const objects, but
  // we will need special handling: we should be able to access only
  // subobjects of such objects that are themselves declared const.
  QualType T = getType(Base);
  return T.isConstQualified() || T->isReferenceType();
}

llvm_unreachable("unknown evaluating decl kind")__builtin_unreachable();
3540}

3542namespace {
3543/// A handle to a complete object (an object that is not a subobject of
3544/// another object).
3545struct CompleteObject {
/// The identity of the object.
APValue::LValueBase Base;
/// The value of the complete object.
APValue *Value;
/// The type of the complete object.
QualType Type;

CompleteObject() : Value(nullptr) {}
CompleteObject(APValue::LValueBase Base, APValue *Value, QualType Type)
    : Base(Base), Value(Value), Type(Type) {}

bool mayAccessMutableMembers(EvalInfo &Info, AccessKinds AK) const {
  // If this isn't a "real" access (eg, if it's just accessing the type
  // info), allow it. We assume the type doesn't change dynamically for
  // subobjects of constexpr objects (even though we'd hit UB here if it
  // did). FIXME: Is this right?
  if (!isAnyAccess(AK))
    return true;

  // In C++14 onwards, it is permitted to read a mutable member whose
  // lifetime began within the evaluation.
  // FIXME: Should we also allow this in C++11?
  if (!Info.getLangOpts().CPlusPlus14)
    return false;
  return lifetimeStartedInEvaluation(Info, Base, /*MutableSubobject*/true);
}

explicit operator bool() const { return !Type.isNull(); }
3574};
3575} // end anonymous namespace

3577static QualType getSubobjectType(QualType ObjType, QualType SubobjType,
                               bool IsMutable = false) {
// C++ [basic.type.qualifier]p1:
// - A const object is an object of type const T or a non-mutable subobject
//   of a const object.
if (ObjType.isConstQualified() && !IsMutable)
  SubobjType.addConst();
// - A volatile object is an object of type const T or a subobject of a
//   volatile object.
if (ObjType.isVolatileQualified())
  SubobjType.addVolatile();
return SubobjType;
3589}

3591/// Find the designated sub-object of an rvalue.
3592template<typename SubobjectHandler>
3593typename SubobjectHandler::result_type
3594findSubobject(EvalInfo &Info, const Expr *E, const CompleteObject &Obj,
            const SubobjectDesignator &Sub, SubobjectHandler &handler) {
if (Sub.Invalid)
  // A diagnostic will have already been produced.
  return handler.failed();
if (Sub.isOnePastTheEnd() || Sub.isMostDerivedAnUnsizedArray()) {
  if (Info.getLangOpts().CPlusPlus11)
    Info.FFDiag(E, Sub.isOnePastTheEnd()
                       ? diag::note_constexpr_access_past_end
                       : diag::note_constexpr_access_unsized_array)
        << handler.AccessKind;
  else
    Info.FFDiag(E);
  return handler.failed();
}

APValue *O = Obj.Value;
QualType ObjType = Obj.Type;
const FieldDecl *LastField = nullptr;
const FieldDecl *VolatileField = nullptr;

// Walk the designator's path to find the subobject.
for (unsigned I = 0, N = Sub.Entries.size(); /**/; ++I) {
  // Reading an indeterminate value is undefined, but assigning over one is OK.
  if ((O->isAbsent() && !(handler.AccessKind == AK_Construct && I == N)) ||
      (O->isIndeterminate() &&
       !isValidIndeterminateAccess(handler.AccessKind))) {
    if (!Info.checkingPotentialConstantExpression())
      Info.FFDiag(E, diag::note_constexpr_access_uninit)
          << handler.AccessKind << O->isIndeterminate();
    return handler.failed();
  }

  // C++ [class.ctor]p5, C++ [class.dtor]p5:
  //    const and volatile semantics are not applied on an object under
  //    {con,de}struction.
  if ((ObjType.isConstQualified() || ObjType.isVolatileQualified()) &&
      ObjType->isRecordType() &&
      Info.isEvaluatingCtorDtor(
          Obj.Base, llvm::makeArrayRef(Sub.Entries.begin(),
                                       Sub.Entries.begin() + I)) !=
                        ConstructionPhase::None) {
    ObjType = Info.Ctx.getCanonicalType(ObjType);
    ObjType.removeLocalConst();
    ObjType.removeLocalVolatile();
  }

  // If this is our last pass, check that the final object type is OK.
  if (I == N || (I == N - 1 && ObjType->isAnyComplexType())) {
    // Accesses to volatile objects are prohibited.
    if (ObjType.isVolatileQualified() && isFormalAccess(handler.AccessKind)) {
      if (Info.getLangOpts().CPlusPlus) {
        int DiagKind;
        SourceLocation Loc;
        const NamedDecl *Decl = nullptr;
        if (VolatileField) {
          DiagKind = 2;
          Loc = VolatileField->getLocation();
          Decl = VolatileField;
        } else if (auto *VD = Obj.Base.dyn_cast<const ValueDecl*>()) {
          DiagKind = 1;
          Loc = VD->getLocation();
          Decl = VD;
        } else {
          DiagKind = 0;
          if (auto *E = Obj.Base.dyn_cast<const Expr *>())
            Loc = E->getExprLoc();
        }
        Info.FFDiag(E, diag::note_constexpr_access_volatile_obj, 1)
            << handler.AccessKind << DiagKind << Decl;
        Info.Note(Loc, diag::note_constexpr_volatile_here) << DiagKind;
      } else {
        Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
      }
      return handler.failed();
    }

    // If we are reading an object of class type, there may still be more
    // things we need to check: if there are any mutable subobjects, we
    // cannot perform this read. (This only happens when performing a trivial
    // copy or assignment.)
    if (ObjType->isRecordType() &&
        !Obj.mayAccessMutableMembers(Info, handler.AccessKind) &&
        diagnoseMutableFields(Info, E, handler.AccessKind, ObjType))
      return handler.failed();
  }

  if (I == N) {
    if (!handler.found(*O, ObjType))
      return false;

    // If we modified a bit-field, truncate it to the right width.
    if (isModification(handler.AccessKind) &&
        LastField && LastField->isBitField() &&
        !truncateBitfieldValue(Info, E, *O, LastField))
      return false;

    return true;
  }

  LastField = nullptr;
  if (ObjType->isArrayType()) {
    // Next subobject is an array element.
    const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(ObjType);
    assert(CAT && "vla in literal type?")((void)0);
    uint64_t Index = Sub.Entries[I].getAsArrayIndex();
    if (CAT->getSize().ule(Index)) {
      // Note, it should not be possible to form a pointer with a valid
      // designator which points more than one past the end of the array.
      if (Info.getLangOpts().CPlusPlus11)
        Info.FFDiag(E, diag::note_constexpr_access_past_end)
          << handler.AccessKind;
      else
        Info.FFDiag(E);
      return handler.failed();
    }

    ObjType = CAT->getElementType();

    if (O->getArrayInitializedElts() > Index)
      O = &O->getArrayInitializedElt(Index);
    else if (!isRead(handler.AccessKind)) {
      expandArray(*O, Index);
      O = &O->getArrayInitializedElt(Index);
    } else
      O = &O->getArrayFiller();
  } else if (ObjType->isAnyComplexType()) {
    // Next subobject is a complex number.
    uint64_t Index = Sub.Entries[I].getAsArrayIndex();
    if (Index > 1) {
      if (Info.getLangOpts().CPlusPlus11)
        Info.FFDiag(E, diag::note_constexpr_access_past_end)
          << handler.AccessKind;
      else
        Info.FFDiag(E);
      return handler.failed();
    }

    ObjType = getSubobjectType(
        ObjType, ObjType->castAs<ComplexType>()->getElementType());

    assert(I == N - 1 && "extracting subobject of scalar?")((void)0);
    if (O->isComplexInt()) {
      return handler.found(Index ? O->getComplexIntImag()
                                 : O->getComplexIntReal(), ObjType);
    } else {
      assert(O->isComplexFloat())((void)0);
      return handler.found(Index ? O->getComplexFloatImag()
                                 : O->getComplexFloatReal(), ObjType);
    }
  } else if (const FieldDecl *Field = getAsField(Sub.Entries[I])) {
    if (Field->isMutable() &&
        !Obj.mayAccessMutableMembers(Info, handler.AccessKind)) {
      Info.FFDiag(E, diag::note_constexpr_access_mutable, 1)
        << handler.AccessKind << Field;
      Info.Note(Field->getLocation(), diag::note_declared_at);
      return handler.failed();
    }

    // Next subobject is a class, struct or union field.
    RecordDecl *RD = ObjType->castAs<RecordType>()->getDecl();
    if (RD->isUnion()) {
      const FieldDecl *UnionField = O->getUnionField();
      if (!UnionField ||
          UnionField->getCanonicalDecl() != Field->getCanonicalDecl()) {
        if (I == N - 1 && handler.AccessKind == AK_Construct) {
          // Placement new onto an inactive union member makes it active.
          O->setUnion(Field, APValue());
        } else {
          // FIXME: If O->getUnionValue() is absent, report that there's no
          // active union member rather than reporting the prior active union
          // member. We'll need to fix nullptr_t to not use APValue() as its
          // representation first.
          Info.FFDiag(E, diag::note_constexpr_access_inactive_union_member)
              << handler.AccessKind << Field << !UnionField << UnionField;
          return handler.failed();
        }
      }
      O = &O->getUnionValue();
    } else
      O = &O->getStructField(Field->getFieldIndex());

    ObjType = getSubobjectType(ObjType, Field->getType(), Field->isMutable());
    LastField = Field;
    if (Field->getType().isVolatileQualified())
      VolatileField = Field;
  } else {
    // Next subobject is a base class.
    const CXXRecordDecl *Derived = ObjType->getAsCXXRecordDecl();
    const CXXRecordDecl *Base = getAsBaseClass(Sub.Entries[I]);
    O = &O->getStructBase(getBaseIndex(Derived, Base));

    ObjType = getSubobjectType(ObjType, Info.Ctx.getRecordType(Base));
  }
}
3789}

3791namespace {
3792struct ExtractSubobjectHandler {
EvalInfo &Info;
const Expr *E;
APValue &Result;
const AccessKinds AccessKind;

typedef bool result_type;
bool failed() { return false; }
bool found(APValue &Subobj, QualType SubobjType) {
  Result = Subobj;
  if (AccessKind == AK_ReadObjectRepresentation)
    return true;
  return CheckFullyInitialized(Info, E->getExprLoc(), SubobjType, Result);
}
bool found(APSInt &Value, QualType SubobjType) {
  Result = APValue(Value);
  return true;
}
bool found(APFloat &Value, QualType SubobjType) {
  Result = APValue(Value);
  return true;
}
3814};
3815} // end anonymous namespace

3817/// Extract the designated sub-object of an rvalue.
3818static bool extractSubobject(EvalInfo &Info, const Expr *E,
                           const CompleteObject &Obj,
                           const SubobjectDesignator &Sub, APValue &Result,
                           AccessKinds AK = AK_Read) {
assert(AK == AK_Read || AK == AK_ReadObjectRepresentation)((void)0);
ExtractSubobjectHandler Handler = {Info, E, Result, AK};
return findSubobject(Info, E, Obj, Sub, Handler);
3825}

3827namespace {
3828struct ModifySubobjectHandler {
EvalInfo &Info;
APValue &NewVal;
const Expr *E;

typedef bool result_type;
static const AccessKinds AccessKind = AK_Assign;

bool checkConst(QualType QT) {
  // Assigning to a const object has undefined behavior.
  if (QT.isConstQualified()) {
    Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
    return false;
  }
  return true;
}

bool failed() { return false; }
bool found(APValue &Subobj, QualType SubobjType) {
  if (!checkConst(SubobjType))
    return false;
  // We've been given ownership of NewVal, so just swap it in.
  Subobj.swap(NewVal);
  return true;
}
bool found(APSInt &Value, QualType SubobjType) {
  if (!checkConst(SubobjType))
    return false;
  if (!NewVal.isInt()) {
    // Maybe trying to write a cast pointer value into a complex?
    Info.FFDiag(E);
    return false;
  }
  Value = NewVal.getInt();
  return true;
}
bool found(APFloat &Value, QualType SubobjType) {
  if (!checkConst(SubobjType))
    return false;
  Value = NewVal.getFloat();
  return true;
}
3870};
3871} // end anonymous namespace

3873const AccessKinds ModifySubobjectHandler::AccessKind;

3875/// Update the designated sub-object of an rvalue to the given value.
3876static bool modifySubobject(EvalInfo &Info, const Expr *E,
                          const CompleteObject &Obj,
                          const SubobjectDesignator &Sub,
                          APValue &NewVal) {
ModifySubobjectHandler Handler = { Info, NewVal, E };
return findSubobject(Info, E, Obj, Sub, Handler);
3882}

3884/// Find the position where two subobject designators diverge, or equivalently
3885/// the length of the common initial subsequence.
3886static unsigned FindDesignatorMismatch(QualType ObjType,
                                     const SubobjectDesignator &A,
                                     const SubobjectDesignator &B,
                                     bool &WasArrayIndex) {
unsigned I = 0, N = std::min(A.Entries.size(), B.Entries.size());
for (/**/; I != N; ++I) {
  if (!ObjType.isNull() &&
      (ObjType->isArrayType() || ObjType->isAnyComplexType())) {
    // Next subobject is an array element.
    if (A.Entries[I].getAsArrayIndex() != B.Entries[I].getAsArrayIndex()) {
      WasArrayIndex = true;
      return I;
    }
    if (ObjType->isAnyComplexType())
      ObjType = ObjType->castAs<ComplexType>()->getElementType();
    else
      ObjType = ObjType->castAsArrayTypeUnsafe()->getElementType();
  } else {
    if (A.Entries[I].getAsBaseOrMember() !=
        B.Entries[I].getAsBaseOrMember()) {
      WasArrayIndex = false;
      return I;
    }
    if (const FieldDecl *FD = getAsField(A.Entries[I]))
      // Next subobject is a field.
      ObjType = FD->getType();
    else
      // Next subobject is a base class.
      ObjType = QualType();
  }
}
WasArrayIndex = false;
return I;
3919}

3921/// Determine whether the given subobject designators refer to elements of the
3922/// same array object.
3923static bool AreElementsOfSameArray(QualType ObjType,
                                 const SubobjectDesignator &A,
                                 const SubobjectDesignator &B) {
if (A.Entries.size() != B.Entries.size())
  return false;

bool IsArray = A.MostDerivedIsArrayElement;
if (IsArray && A.MostDerivedPathLength != A.Entries.size())
  // A is a subobject of the array element.
  return false;

// If A (and B) designates an array element, the last entry will be the array
// index. That doesn't have to match. Otherwise, we're in the 'implicit array
// of length 1' case, and the entire path must match.
bool WasArrayIndex;
unsigned CommonLength = FindDesignatorMismatch(ObjType, A, B, WasArrayIndex);
return CommonLength >= A.Entries.size() - IsArray;
3940}

3942/// Find the complete object to which an LValue refers.
3943static CompleteObject findCompleteObject(EvalInfo &Info, const Expr *E,
                                       AccessKinds AK, const LValue &LVal,
                                       QualType LValType) {
if (LVal.InvalidBase) {
  Info.FFDiag(E);
  return CompleteObject();
}

if (!LVal.Base) {
  Info.FFDiag(E, diag::note_constexpr_access_null) << AK;
  return CompleteObject();
}

CallStackFrame *Frame = nullptr;
unsigned Depth = 0;
if (LVal.getLValueCallIndex()) {
  std::tie(Frame, Depth) =
      Info.getCallFrameAndDepth(LVal.getLValueCallIndex());
  if (!Frame) {
    Info.FFDiag(E, diag::note_constexpr_lifetime_ended, 1)
      << AK << LVal.Base.is<const ValueDecl*>();
    NoteLValueLocation(Info, LVal.Base);
    return CompleteObject();
  }
}

bool IsAccess = isAnyAccess(AK);

// C++11 DR1311: An lvalue-to-rvalue conversion on a volatile-qualified type
// is not a constant expression (even if the object is non-volatile). We also
// apply this rule to C++98, in order to conform to the expected 'volatile'
// semantics.
if (isFormalAccess(AK) && LValType.isVolatileQualified()) {
  if (Info.getLangOpts().CPlusPlus)
    Info.FFDiag(E, diag::note_constexpr_access_volatile_type)
      << AK << LValType;
  else
    Info.FFDiag(E);
  return CompleteObject();
}

// Compute value storage location and type of base object.
APValue *BaseVal = nullptr;
QualType BaseType = getType(LVal.Base);

if (Info.getLangOpts().CPlusPlus14 && LVal.Base == Info.EvaluatingDecl &&
    lifetimeStartedInEvaluation(Info, LVal.Base)) {
  // This is the object whose initializer we're evaluating, so its lifetime
  // started in the current evaluation.
  BaseVal = Info.EvaluatingDeclValue;
} else if (const ValueDecl *D = LVal.Base.dyn_cast<const ValueDecl *>()) {
  // Allow reading from a GUID declaration.
  if (auto *GD = dyn_cast<MSGuidDecl>(D)) {
    if (isModification(AK)) {
      // All the remaining cases do not permit modification of the object.
      Info.FFDiag(E, diag::note_constexpr_modify_global);
      return CompleteObject();
    }
    APValue &V = GD->getAsAPValue();
    if (V.isAbsent()) {
      Info.FFDiag(E, diag::note_constexpr_unsupported_layout)
          << GD->getType();
      return CompleteObject();
    }
    return CompleteObject(LVal.Base, &V, GD->getType());
  }

  // Allow reading from template parameter objects.
  if (auto *TPO = dyn_cast<TemplateParamObjectDecl>(D)) {
    if (isModification(AK)) {
      Info.FFDiag(E, diag::note_constexpr_modify_global);
      return CompleteObject();
    }
    return CompleteObject(LVal.Base, const_cast<APValue *>(&TPO->getValue()),
                          TPO->getType());
  }

  // In C++98, const, non-volatile integers initialized with ICEs are ICEs.
  // In C++11, constexpr, non-volatile variables initialized with constant
  // expressions are constant expressions too. Inside constexpr functions,
  // parameters are constant expressions even if they're non-const.
  // In C++1y, objects local to a constant expression (those with a Frame) are
  // both readable and writable inside constant expressions.
  // In C, such things can also be folded, although they are not ICEs.
  const VarDecl *VD = dyn_cast<VarDecl>(D);
  if (VD) {
    if (const VarDecl *VDef = VD->getDefinition(Info.Ctx))
      VD = VDef;
  }
  if (!VD || VD->isInvalidDecl()) {
    Info.FFDiag(E);
    return CompleteObject();
  }

  bool IsConstant = BaseType.isConstant(Info.Ctx);

  // Unless we're looking at a local variable or argument in a constexpr call,
  // the variable we're reading must be const.
  if (!Frame) {
    if (IsAccess && isa<ParmVarDecl>(VD)) {
      // Access of a parameter that's not associated with a frame isn't going
      // to work out, but we can leave it to evaluateVarDeclInit to provide a
      // suitable diagnostic.
    } else if (Info.getLangOpts().CPlusPlus14 &&
               lifetimeStartedInEvaluation(Info, LVal.Base)) {
      // OK, we can read and modify an object if we're in the process of
      // evaluating its initializer, because its lifetime began in this
      // evaluation.
    } else if (isModification(AK)) {
      // All the remaining cases do not permit modification of the object.
      Info.FFDiag(E, diag::note_constexpr_modify_global);
      return CompleteObject();
    } else if (VD->isConstexpr()) {
      // OK, we can read this variable.
    } else if (BaseType->isIntegralOrEnumerationType()) {
      if (!IsConstant) {
        if (!IsAccess)
          return CompleteObject(LVal.getLValueBase(), nullptr, BaseType);
        if (Info.getLangOpts().CPlusPlus) {
          Info.FFDiag(E, diag::note_constexpr_ltor_non_const_int, 1) << VD;
          Info.Note(VD->getLocation(), diag::note_declared_at);
        } else {
          Info.FFDiag(E);
        }
        return CompleteObject();
      }
    } else if (!IsAccess) {
      return CompleteObject(LVal.getLValueBase(), nullptr, BaseType);
    } else if (IsConstant && Info.checkingPotentialConstantExpression() &&
               BaseType->isLiteralType(Info.Ctx) && !VD->hasDefinition()) {
      // This variable might end up being constexpr. Don't diagnose it yet.
    } else if (IsConstant) {
      // Keep evaluating to see what we can do. In particular, we support
      // folding of const floating-point types, in order to make static const
      // data members of such types (supported as an extension) more useful.
      if (Info.getLangOpts().CPlusPlus) {
        Info.CCEDiag(E, Info.getLangOpts().CPlusPlus11
                            ? diag::note_constexpr_ltor_non_constexpr
                            : diag::note_constexpr_ltor_non_integral, 1)
            << VD << BaseType;
        Info.Note(VD->getLocation(), diag::note_declared_at);
      } else {
        Info.CCEDiag(E);
      }
    } else {
      // Never allow reading a non-const value.
      if (Info.getLangOpts().CPlusPlus) {
        Info.FFDiag(E, Info.getLangOpts().CPlusPlus11
                           ? diag::note_constexpr_ltor_non_constexpr
                           : diag::note_constexpr_ltor_non_integral, 1)
            << VD << BaseType;
        Info.Note(VD->getLocation(), diag::note_declared_at);
      } else {
        Info.FFDiag(E);
      }
      return CompleteObject();
    }
  }

  if (!evaluateVarDeclInit(Info, E, VD, Frame, LVal.getLValueVersion(), BaseVal))
    return CompleteObject();
} else if (DynamicAllocLValue DA = LVal.Base.dyn_cast<DynamicAllocLValue>()) {
  Optional<DynAlloc*> Alloc = Info.lookupDynamicAlloc(DA);
  if (!Alloc) {
    Info.FFDiag(E, diag::note_constexpr_access_deleted_object) << AK;
    return CompleteObject();
  }
  return CompleteObject(LVal.Base, &(*Alloc)->Value,
                        LVal.Base.getDynamicAllocType());
} else {
  const Expr *Base = LVal.Base.dyn_cast<const Expr*>();

  if (!Frame) {
    if (const MaterializeTemporaryExpr *MTE =
            dyn_cast_or_null<MaterializeTemporaryExpr>(Base)) {
      assert(MTE->getStorageDuration() == SD_Static &&((void)0)
             "should have a frame for a non-global materialized temporary")((void)0);

      // C++20 [expr.const]p4: [DR2126]
      //   An object or reference is usable in constant expressions if it is
      //   - a temporary object of non-volatile const-qualified literal type
      //     whose lifetime is extended to that of a variable that is usable
      //     in constant expressions
      //
      // C++20 [expr.const]p5:
      //  an lvalue-to-rvalue conversion [is not allowed unless it applies to]
      //   - a non-volatile glvalue that refers to an object that is usable
      //     in constant expressions, or
      //   - a non-volatile glvalue of literal type that refers to a
      //     non-volatile object whose lifetime began within the evaluation
      //     of E;
      //
      // C++11 misses the 'began within the evaluation of e' check and
      // instead allows all temporaries, including things like:
      //   int &&r = 1;
      //   int x = ++r;
      //   constexpr int k = r;
      // Therefore we use the C++14-onwards rules in C++11 too.
      //
      // Note that temporaries whose lifetimes began while evaluating a
      // variable's constructor are not usable while evaluating the
      // corresponding destructor, not even if they're of const-qualified
      // types.
      if (!MTE->isUsableInConstantExpressions(Info.Ctx) &&
          !lifetimeStartedInEvaluation(Info, LVal.Base)) {
        if (!IsAccess)
          return CompleteObject(LVal.getLValueBase(), nullptr, BaseType);
        Info.FFDiag(E, diag::note_constexpr_access_static_temporary, 1) << AK;
        Info.Note(MTE->getExprLoc(), diag::note_constexpr_temporary_here);
        return CompleteObject();
      }

      BaseVal = MTE->getOrCreateValue(false);
      assert(BaseVal && "got reference to unevaluated temporary")((void)0);
    } else {
      if (!IsAccess)
        return CompleteObject(LVal.getLValueBase(), nullptr, BaseType);
      APValue Val;
      LVal.moveInto(Val);
      Info.FFDiag(E, diag::note_constexpr_access_unreadable_object)
          << AK
          << Val.getAsString(Info.Ctx,
                             Info.Ctx.getLValueReferenceType(LValType));
      NoteLValueLocation(Info, LVal.Base);
      return CompleteObject();
    }
  } else {
    BaseVal = Frame->getTemporary(Base, LVal.Base.getVersion());
    assert(BaseVal && "missing value for temporary")((void)0);
  }
}

// In C++14, we can't safely access any mutable state when we might be
// evaluating after an unmodeled side effect. Parameters are modeled as state
// in the caller, but aren't visible once the call returns, so they can be
// modified in a speculatively-evaluated call.
//
// FIXME: Not all local state is mutable. Allow local constant subobjects
// to be read here (but take care with 'mutable' fields).
unsigned VisibleDepth = Depth;
if (llvm::isa_and_nonnull<ParmVarDecl>(
        LVal.Base.dyn_cast<const ValueDecl *>()))
  ++VisibleDepth;
if ((Frame && Info.getLangOpts().CPlusPlus14 &&
     Info.EvalStatus.HasSideEffects) ||
    (isModification(AK) && VisibleDepth < Info.SpeculativeEvaluationDepth))
  return CompleteObject();

return CompleteObject(LVal.getLValueBase(), BaseVal, BaseType);
4192}

4194/// Perform an lvalue-to-rvalue conversion on the given glvalue. This
4195/// can also be used for 'lvalue-to-lvalue' conversions for looking up the
4196/// glvalue referred to by an entity of reference type.
4197///
4198/// \param Info - Information about the ongoing evaluation.
4199/// \param Conv - The expression for which we are performing the conversion.
4200///               Used for diagnostics.
4201/// \param Type - The type of the glvalue (before stripping cv-qualifiers in the
4202///               case of a non-class type).
4203/// \param LVal - The glvalue on which we are attempting to perform this action.
4204/// \param RVal - The produced value will be placed here.
4205/// \param WantObjectRepresentation - If true, we're looking for the object
4206///               representation rather than the value, and in particular,
4207///               there is no requirement that the result be fully initialized.
4208static bool
4209handleLValueToRValueConversion(EvalInfo &Info, const Expr *Conv, QualType Type,
                             const LValue &LVal, APValue &RVal,
                             bool WantObjectRepresentation = false) {
if (LVal.Designator.Invalid)
69
←
Assuming field 'Invalid' is 0→
70
←
Taking false branch→
  return false;

// Check for special cases where there is no existing APValue to look at.
const Expr *Base = LVal.Base.dyn_cast<const Expr*>();
71
←
Calling 'LValueBase::dyn_cast'→
81
←
Returning from 'LValueBase::dyn_cast'→

AccessKinds AK =
    WantObjectRepresentation81.1
'WantObjectRepresentation' is false
1
'WantObjectRepresentation' is false
1
'WantObjectRepresentation' is false
1
'WantObjectRepresentation' is false
1
'WantObjectRepresentation' is false
1
'WantObjectRepresentation' is false
 ? AK_ReadObjectRepresentation : AK_Read;
82
←
'?' condition is false→

if (Base82.1
'Base' is null
1
'Base' is null
1
'Base' is null
1
'Base' is null
1
'Base' is null
1
'Base' is null
 && !LVal.getLValueCallIndex() && !Type.isVolatileQualified()) {
  if (const CompoundLiteralExpr *CLE = dyn_cast<CompoundLiteralExpr>(Base)) {
    // In C99, a CompoundLiteralExpr is an lvalue, and we defer evaluating the
    // initializer until now for such expressions. Such an expression can't be
    // an ICE in C, so this only matters for fold.
    if (Type.isVolatileQualified()) {
      Info.FFDiag(Conv);
      return false;
    }
    APValue Lit;
    if (!Evaluate(Lit, Info, CLE->getInitializer()))
      return false;
    CompleteObject LitObj(LVal.Base, &Lit, Base->getType());
    return extractSubobject(Info, Conv, LitObj, LVal.Designator, RVal, AK);
  } else if (isa<StringLiteral>(Base) || isa<PredefinedExpr>(Base)) {
    // Special-case character extraction so we don't have to construct an
    // APValue for the whole string.
    assert(LVal.Designator.Entries.size() <= 1 &&((void)0)
           "Can only read characters from string literals")((void)0);
    if (LVal.Designator.Entries.empty()) {
      // Fail for now for LValue to RValue conversion of an array.
      // (This shouldn't show up in C/C++, but it could be triggered by a
      // weird EvaluateAsRValue call from a tool.)
      Info.FFDiag(Conv);
      return false;
    }
    if (LVal.Designator.isOnePastTheEnd()) {
      if (Info.getLangOpts().CPlusPlus11)
        Info.FFDiag(Conv, diag::note_constexpr_access_past_end) << AK;
      else
        Info.FFDiag(Conv);
      return false;
    }
    uint64_t CharIndex = LVal.Designator.Entries[0].getAsArrayIndex();
    RVal = APValue(extractStringLiteralCharacter(Info, Base, CharIndex));
    return true;
  }
}

CompleteObject Obj = findCompleteObject(Info, Conv, AK, LVal, Type);
return Obj && extractSubobject(Info, Conv, Obj, LVal.Designator, RVal, AK);
83
←
Returning value, which participates in a condition later→
4262}

4264/// Perform an assignment of Val to LVal. Takes ownership of Val.
4265static bool handleAssignment(EvalInfo &Info, const Expr *E, const LValue &LVal,
                           QualType LValType, APValue &Val) {
if (LVal.Designator.Invalid)
  return false;

if (!Info.getLangOpts().CPlusPlus14) {
  Info.FFDiag(E);
  return false;
}

CompleteObject Obj = findCompleteObject(Info, E, AK_Assign, LVal, LValType);
return Obj && modifySubobject(Info, E, Obj, LVal.Designator, Val);
4277}

4279namespace {
4280struct CompoundAssignSubobjectHandler {
EvalInfo &Info;
const CompoundAssignOperator *E;
QualType PromotedLHSType;
BinaryOperatorKind Opcode;
const APValue &RHS;

static const AccessKinds AccessKind = AK_Assign;

typedef bool result_type;

bool checkConst(QualType QT) {
  // Assigning to a const object has undefined behavior.
  if (QT.isConstQualified()) {
    Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
    return false;
  }
  return true;
}

bool failed() { return false; }
bool found(APValue &Subobj, QualType SubobjType) {
  switch (Subobj.getKind()) {
  case APValue::Int:
    return found(Subobj.getInt(), SubobjType);
  case APValue::Float:
    return found(Subobj.getFloat(), SubobjType);
  case APValue::ComplexInt:
  case APValue::ComplexFloat:
    // FIXME: Implement complex compound assignment.
    Info.FFDiag(E);
    return false;
  case APValue::LValue:
    return foundPointer(Subobj, SubobjType);
  case APValue::Vector:
    return foundVector(Subobj, SubobjType);
  default:
    // FIXME: can this happen?
    Info.FFDiag(E);
    return false;
  }
}

bool foundVector(APValue &Value, QualType SubobjType) {
  if (!checkConst(SubobjType))
    return false;

  if (!SubobjType->isVectorType()) {
    Info.FFDiag(E);
    return false;
  }
  return handleVectorVectorBinOp(Info, E, Opcode, Value, RHS);
}

bool found(APSInt &Value, QualType SubobjType) {
  if (!checkConst(SubobjType))
    return false;

  if (!SubobjType->isIntegerType()) {
    // We don't support compound assignment on integer-cast-to-pointer
    // values.
    Info.FFDiag(E);
    return false;
  }

  if (RHS.isInt()) {
    APSInt LHS =
        HandleIntToIntCast(Info, E, PromotedLHSType, SubobjType, Value);
    if (!handleIntIntBinOp(Info, E, LHS, Opcode, RHS.getInt(), LHS))
      return false;
    Value = HandleIntToIntCast(Info, E, SubobjType, PromotedLHSType, LHS);
    return true;
  } else if (RHS.isFloat()) {
    const FPOptions FPO = E->getFPFeaturesInEffect(
                                  Info.Ctx.getLangOpts());
    APFloat FValue(0.0);
    return HandleIntToFloatCast(Info, E, FPO, SubobjType, Value,
                                PromotedLHSType, FValue) &&
           handleFloatFloatBinOp(Info, E, FValue, Opcode, RHS.getFloat()) &&
           HandleFloatToIntCast(Info, E, PromotedLHSType, FValue, SubobjType,
                                Value);
  }

  Info.FFDiag(E);
  return false;
}
bool found(APFloat &Value, QualType SubobjType) {
  return checkConst(SubobjType) &&
         HandleFloatToFloatCast(Info, E, SubobjType, PromotedLHSType,
                                Value) &&
         handleFloatFloatBinOp(Info, E, Value, Opcode, RHS.getFloat()) &&
         HandleFloatToFloatCast(Info, E, PromotedLHSType, SubobjType, Value);
}
bool foundPointer(APValue &Subobj, QualType SubobjType) {
  if (!checkConst(SubobjType))
    return false;

  QualType PointeeType;
  if (const PointerType *PT = SubobjType->getAs<PointerType>())
    PointeeType = PT->getPointeeType();

  if (PointeeType.isNull() || !RHS.isInt() ||
      (Opcode != BO_Add && Opcode != BO_Sub)) {
    Info.FFDiag(E);
    return false;
  }

  APSInt Offset = RHS.getInt();
  if (Opcode == BO_Sub)
    negateAsSigned(Offset);

  LValue LVal;
  LVal.setFrom(Info.Ctx, Subobj);
  if (!HandleLValueArrayAdjustment(Info, E, LVal, PointeeType, Offset))
    return false;
  LVal.moveInto(Subobj);
  return true;
}
4398};
4399} // end anonymous namespace

4401const AccessKinds CompoundAssignSubobjectHandler::AccessKind;

4403/// Perform a compound assignment of LVal <op>= RVal.
4404static bool handleCompoundAssignment(EvalInfo &Info,
                                   const CompoundAssignOperator *E,
                                   const LValue &LVal, QualType LValType,
                                   QualType PromotedLValType,
                                   BinaryOperatorKind Opcode,
                                   const APValue &RVal) {
if (LVal.Designator.Invalid)
  return false;

if (!Info.getLangOpts().CPlusPlus14) {
  Info.FFDiag(E);
  return false;
}

CompleteObject Obj = findCompleteObject(Info, E, AK_Assign, LVal, LValType);
CompoundAssignSubobjectHandler Handler = { Info, E, PromotedLValType, Opcode,
                                           RVal };
return Obj && findSubobject(Info, E, Obj, LVal.Designator, Handler);
4422}

4424namespace {
4425struct IncDecSubobjectHandler {
EvalInfo &Info;
const UnaryOperator *E;
AccessKinds AccessKind;
APValue *Old;

typedef bool result_type;

bool checkConst(QualType QT) {
  // Assigning to a const object has undefined behavior.
  if (QT.isConstQualified()) {
    Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
    return false;
  }
  return true;
}

bool failed() { return false; }
bool found(APValue &Subobj, QualType SubobjType) {
  // Stash the old value. Also clear Old, so we don't clobber it later
  // if we're post-incrementing a complex.
  if (Old) {
    *Old = Subobj;
    Old = nullptr;
  }

  switch (Subobj.getKind()) {
  case APValue::Int:
    return found(Subobj.getInt(), SubobjType);
  case APValue::Float:
    return found(Subobj.getFloat(), SubobjType);
  case APValue::ComplexInt:
    return found(Subobj.getComplexIntReal(),
                 SubobjType->castAs<ComplexType>()->getElementType()
                   .withCVRQualifiers(SubobjType.getCVRQualifiers()));
  case APValue::ComplexFloat:
    return found(Subobj.getComplexFloatReal(),
                 SubobjType->castAs<ComplexType>()->getElementType()
                   .withCVRQualifiers(SubobjType.getCVRQualifiers()));
  case APValue::LValue:
    return foundPointer(Subobj, SubobjType);
  default:
    // FIXME: can this happen?
    Info.FFDiag(E);
    return false;
  }
}
bool found(APSInt &Value, QualType SubobjType) {
  if (!checkConst(SubobjType))
    return false;

  if (!SubobjType->isIntegerType()) {
    // We don't support increment / decrement on integer-cast-to-pointer
    // values.
    Info.FFDiag(E);
    return false;
  }

  if (Old) *Old = APValue(Value);

  // bool arithmetic promotes to int, and the conversion back to bool
  // doesn't reduce mod 2^n, so special-case it.
  if (SubobjType->isBooleanType()) {
    if (AccessKind == AK_Increment)
      Value = 1;
    else
      Value = !Value;
    return true;
  }

  bool WasNegative = Value.isNegative();
  if (AccessKind == AK_Increment) {
    ++Value;

    if (!WasNegative && Value.isNegative() && E->canOverflow()) {
      APSInt ActualValue(Value, /*IsUnsigned*/true);
      return HandleOverflow(Info, E, ActualValue, SubobjType);
    }
  } else {
    --Value;

    if (WasNegative && !Value.isNegative() && E->canOverflow()) {
      unsigned BitWidth = Value.getBitWidth();
      APSInt ActualValue(Value.sext(BitWidth + 1), /*IsUnsigned*/false);
      ActualValue.setBit(BitWidth);
      return HandleOverflow(Info, E, ActualValue, SubobjType);
    }
  }
  return true;
}
bool found(APFloat &Value, QualType SubobjType) {
  if (!checkConst(SubobjType))
    return false;

  if (Old) *Old = APValue(Value);

  APFloat One(Value.getSemantics(), 1);
  if (AccessKind == AK_Increment)
    Value.add(One, APFloat::rmNearestTiesToEven);
  else
    Value.subtract(One, APFloat::rmNearestTiesToEven);
  return true;
}
bool foundPointer(APValue &Subobj, QualType SubobjType) {
  if (!checkConst(SubobjType))
    return false;

  QualType PointeeType;
  if (const PointerType *PT = SubobjType->getAs<PointerType>())
    PointeeType = PT->getPointeeType();
  else {
    Info.FFDiag(E);
    return false;
  }

  LValue LVal;
  LVal.setFrom(Info.Ctx, Subobj);
  if (!HandleLValueArrayAdjustment(Info, E, LVal, PointeeType,
                                   AccessKind == AK_Increment ? 1 : -1))
    return false;
  LVal.moveInto(Subobj);
  return true;
}
4548};
4549} // end anonymous namespace

4551/// Perform an increment or decrement on LVal.
4552static bool handleIncDec(EvalInfo &Info, const Expr *E, const LValue &LVal,
                       QualType LValType, bool IsIncrement, APValue *Old) {
if (LVal.Designator.Invalid)
  return false;

if (!Info.getLangOpts().CPlusPlus14) {
  Info.FFDiag(E);
  return false;
}

AccessKinds AK = IsIncrement ? AK_Increment : AK_Decrement;
CompleteObject Obj = findCompleteObject(Info, E, AK, LVal, LValType);
IncDecSubobjectHandler Handler = {Info, cast<UnaryOperator>(E), AK, Old};
return Obj && findSubobject(Info, E, Obj, LVal.Designator, Handler);
4566}

4568/// Build an lvalue for the object argument of a member function call.
4569static bool EvaluateObjectArgument(EvalInfo &Info, const Expr *Object,
                                 LValue &This) {
if (Object->getType()->isPointerType() && Object->isPRValue())
  return EvaluatePointer(Object, This, Info);

if (Object->isGLValue())
  return EvaluateLValue(Object, This, Info);

if (Object->getType()->isLiteralType(Info.Ctx))
  return EvaluateTemporary(Object, This, Info);

Info.FFDiag(Object, diag::note_constexpr_nonliteral) << Object->getType();
return false;
4582}

4584/// HandleMemberPointerAccess - Evaluate a member access operation and build an
4585/// lvalue referring to the result.
4586///
4587/// \param Info - Information about the ongoing evaluation.
4588/// \param LV - An lvalue referring to the base of the member pointer.
4589/// \param RHS - The member pointer expression.
4590/// \param IncludeMember - Specifies whether the member itself is included in
4591///        the resulting LValue subobject designator. This is not possible when
4592///        creating a bound member function.
4593/// \return The field or method declaration to which the member pointer refers,
4594///         or 0 if evaluation fails.
4595static const ValueDecl *HandleMemberPointerAccess(EvalInfo &Info,
                                                QualType LVType,
                                                LValue &LV,
                                                const Expr *RHS,
                                                bool IncludeMember = true) {
MemberPtr MemPtr;
if (!EvaluateMemberPointer(RHS, MemPtr, Info))
  return nullptr;

// C++11 [expr.mptr.oper]p6: If the second operand is the null pointer to
// member value, the behavior is undefined.
if (!MemPtr.getDecl()) {
  // FIXME: Specific diagnostic.
  Info.FFDiag(RHS);
  return nullptr;
}

if (MemPtr.isDerivedMember()) {
  // This is a member of some derived class. Truncate LV appropriately.
  // The end of the derived-to-base path for the base object must match the
  // derived-to-base path for the member pointer.
  if (LV.Designator.MostDerivedPathLength + MemPtr.Path.size() >
      LV.Designator.Entries.size()) {
    Info.FFDiag(RHS);
    return nullptr;
  }
  unsigned PathLengthToMember =
      LV.Designator.Entries.size() - MemPtr.Path.size();
  for (unsigned I = 0, N = MemPtr.Path.size(); I != N; ++I) {
    const CXXRecordDecl *LVDecl = getAsBaseClass(
        LV.Designator.Entries[PathLengthToMember + I]);
    const CXXRecordDecl *MPDecl = MemPtr.Path[I];
    if (LVDecl->getCanonicalDecl() != MPDecl->getCanonicalDecl()) {
      Info.FFDiag(RHS);
      return nullptr;
    }
  }

  // Truncate the lvalue to the appropriate derived class.
  if (!CastToDerivedClass(Info, RHS, LV, MemPtr.getContainingRecord(),
                          PathLengthToMember))
    return nullptr;
} else if (!MemPtr.Path.empty()) {
  // Extend the LValue path with the member pointer's path.
  LV.Designator.Entries.reserve(LV.Designator.Entries.size() +
                                MemPtr.Path.size() + IncludeMember);

  // Walk down to the appropriate base class.
  if (const PointerType *PT = LVType->getAs<PointerType>())
    LVType = PT->getPointeeType();
  const CXXRecordDecl *RD = LVType->getAsCXXRecordDecl();
  assert(RD && "member pointer access on non-class-type expression")((void)0);
  // The first class in the path is that of the lvalue.
  for (unsigned I = 1, N = MemPtr.Path.size(); I != N; ++I) {
    const CXXRecordDecl *Base = MemPtr.Path[N - I - 1];
    if (!HandleLValueDirectBase(Info, RHS, LV, RD, Base))
      return nullptr;
    RD = Base;
  }
  // Finally cast to the class containing the member.
  if (!HandleLValueDirectBase(Info, RHS, LV, RD,
                              MemPtr.getContainingRecord()))
    return nullptr;
}

// Add the member. Note that we cannot build bound member functions here.
if (IncludeMember) {
  if (const FieldDecl *FD = dyn_cast<FieldDecl>(MemPtr.getDecl())) {
    if (!HandleLValueMember(Info, RHS, LV, FD))
      return nullptr;
  } else if (const IndirectFieldDecl *IFD =
               dyn_cast<IndirectFieldDecl>(MemPtr.getDecl())) {
    if (!HandleLValueIndirectMember(Info, RHS, LV, IFD))
      return nullptr;
  } else {
    llvm_unreachable("can't construct reference to bound member function")__builtin_unreachable();
  }
}

return MemPtr.getDecl();
4675}

4677static const ValueDecl *HandleMemberPointerAccess(EvalInfo &Info,
                                                const BinaryOperator *BO,
                                                LValue &LV,
                                                bool IncludeMember = true) {
assert(BO->getOpcode() == BO_PtrMemD || BO->getOpcode() == BO_PtrMemI)((void)0);

if (!EvaluateObjectArgument(Info, BO->getLHS(), LV)) {
  if (Info.noteFailure()) {
    MemberPtr MemPtr;
    EvaluateMemberPointer(BO->getRHS(), MemPtr, Info);
  }
  return nullptr;
}

return HandleMemberPointerAccess(Info, BO->getLHS()->getType(), LV,
                                 BO->getRHS(), IncludeMember);
4693}

4695/// HandleBaseToDerivedCast - Apply the given base-to-derived cast operation on
4696/// the provided lvalue, which currently refers to the base object.
4697static bool HandleBaseToDerivedCast(EvalInfo &Info, const CastExpr *E,
                                  LValue &Result) {
SubobjectDesignator &D = Result.Designator;
if (D.Invalid || !Result.checkNullPointer(Info, E, CSK_Derived))
  return false;

QualType TargetQT = E->getType();
if (const PointerType *PT = TargetQT->getAs<PointerType>())
  TargetQT = PT->getPointeeType();

// Check this cast lands within the final derived-to-base subobject path.
if (D.MostDerivedPathLength + E->path_size() > D.Entries.size()) {
  Info.CCEDiag(E, diag::note_constexpr_invalid_downcast)
    << D.MostDerivedType << TargetQT;
  return false;
}

// Check the type of the final cast. We don't need to check the path,
// since a cast can only be formed if the path is unique.
unsigned NewEntriesSize = D.Entries.size() - E->path_size();
const CXXRecordDecl *TargetType = TargetQT->getAsCXXRecordDecl();
const CXXRecordDecl *FinalType;
if (NewEntriesSize == D.MostDerivedPathLength)
  FinalType = D.MostDerivedType->getAsCXXRecordDecl();
else
  FinalType = getAsBaseClass(D.Entries[NewEntriesSize - 1]);
if (FinalType->getCanonicalDecl() != TargetType->getCanonicalDecl()) {
  Info.CCEDiag(E, diag::note_constexpr_invalid_downcast)
    << D.MostDerivedType << TargetQT;
  return false;
}

// Truncate the lvalue to the appropriate derived class.
return CastToDerivedClass(Info, E, Result, TargetType, NewEntriesSize);
4731}

4733/// Get the value to use for a default-initialized object of type T.
4734/// Return false if it encounters something invalid.
4735static bool getDefaultInitValue(QualType T, APValue &Result) {
bool Success = true;
if (auto *RD = T->getAsCXXRecordDecl()) {
  if (RD->isInvalidDecl()) {
    Result = APValue();
    return false;
  }
  if (RD->isUnion()) {
    Result = APValue((const FieldDecl *)nullptr);
    return true;
  }
  Result = APValue(APValue::UninitStruct(), RD->getNumBases(),
                   std::distance(RD->field_begin(), RD->field_end()));

  unsigned Index = 0;
  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
                                                End = RD->bases_end();
       I != End; ++I, ++Index)
    Success &= getDefaultInitValue(I->getType(), Result.getStructBase(Index));

  for (const auto *I : RD->fields()) {
    if (I->isUnnamedBitfield())
      continue;
    Success &= getDefaultInitValue(I->getType(),
                                   Result.getStructField(I->getFieldIndex()));
  }
  return Success;
}

if (auto *AT =
        dyn_cast_or_null<ConstantArrayType>(T->getAsArrayTypeUnsafe())) {
  Result = APValue(APValue::UninitArray(), 0, AT->getSize().getZExtValue());
  if (Result.hasArrayFiller())
    Success &=
        getDefaultInitValue(AT->getElementType(), Result.getArrayFiller());

  return Success;
}

Result = APValue::IndeterminateValue();
return true;
4776}

4778namespace {
4779enum EvalStmtResult {
/// Evaluation failed.
ESR_Failed,
/// Hit a 'return' statement.
ESR_Returned,
/// Evaluation succeeded.
ESR_Succeeded,
/// Hit a 'continue' statement.
ESR_Continue,
/// Hit a 'break' statement.
ESR_Break,
/// Still scanning for 'case' or 'default' statement.
ESR_CaseNotFound
4792};
4793}

4795static bool EvaluateVarDecl(EvalInfo &Info, const VarDecl *VD) {
// We don't need to evaluate the initializer for a static local.
if (!VD->hasLocalStorage())
  return true;

LValue Result;
APValue &Val = Info.CurrentCall->createTemporary(VD, VD->getType(),
                                                 ScopeKind::Block, Result);

const Expr *InitE = VD->getInit();
if (!InitE) {
  if (VD->getType()->isDependentType())
    return Info.noteSideEffect();
  return getDefaultInitValue(VD->getType(), Val);
}
if (InitE->isValueDependent())
  return false;

if (!EvaluateInPlace(Val, Info, Result, InitE)) {
  // Wipe out any partially-computed value, to allow tracking that this
  // evaluation failed.
  Val = APValue();
  return false;
}

return true;
4821}

4823static bool EvaluateDecl(EvalInfo &Info, const Decl *D) {
bool OK = true;

if (const VarDecl *VD = dyn_cast<VarDecl>(D))
  OK &= EvaluateVarDecl(Info, VD);

if (const DecompositionDecl *DD = dyn_cast<DecompositionDecl>(D))
  for (auto *BD : DD->bindings())
    if (auto *VD = BD->getHoldingVar())
      OK &= EvaluateDecl(Info, VD);

return OK;
4835}

4837static bool EvaluateDependentExpr(const Expr *E, EvalInfo &Info) {
assert(E->isValueDependent())((void)0);
if (Info.noteSideEffect())
  return true;
assert(E->containsErrors() && "valid value-dependent expression should never "((void)0)
                              "reach invalid code path.")((void)0);
return false;
4844}

4846/// Evaluate a condition (either a variable declaration or an expression).
4847static bool EvaluateCond(EvalInfo &Info, const VarDecl *CondDecl,
                       const Expr *Cond, bool &Result) {
if (Cond->isValueDependent())
  return false;
FullExpressionRAII Scope(Info);
if (CondDecl && !EvaluateDecl(Info, CondDecl))
  return false;
if (!EvaluateAsBooleanCondition(Cond, Result, Info))
  return false;
return Scope.destroy();
4857}

4859namespace {
4860/// A location where the result (returned value) of evaluating a
4861/// statement should be stored.
4862struct StmtResult {
/// The APValue that should be filled in with the returned value.
APValue &Value;
/// The location containing the result, if any (used to support RVO).
const LValue *Slot;
4867};

4869struct TempVersionRAII {
CallStackFrame &Frame;

TempVersionRAII(CallStackFrame &Frame) : Frame(Frame) {
  Frame.pushTempVersion();
}

~TempVersionRAII() {
  Frame.popTempVersion();
}
4879};

4881}

4883static EvalStmtResult EvaluateStmt(StmtResult &Result, EvalInfo &Info,
                                 const Stmt *S,
                                 const SwitchCase *SC = nullptr);

4887/// Evaluate the body of a loop, and translate the result as appropriate.
4888static EvalStmtResult EvaluateLoopBody(StmtResult &Result, EvalInfo &Info,
                                     const Stmt *Body,
                                     const SwitchCase *Case = nullptr) {
BlockScopeRAII Scope(Info);

EvalStmtResult ESR = EvaluateStmt(Result, Info, Body, Case);
if (ESR != ESR_Failed && ESR != ESR_CaseNotFound && !Scope.destroy())
  ESR = ESR_Failed;

switch (ESR) {
case ESR_Break:
  return ESR_Succeeded;
case ESR_Succeeded:
case ESR_Continue:
  return ESR_Continue;
case ESR_Failed:
case ESR_Returned:
case ESR_CaseNotFound:
  return ESR;
}
llvm_unreachable("Invalid EvalStmtResult!")__builtin_unreachable();
4909}

4911/// Evaluate a switch statement.
4912static EvalStmtResult EvaluateSwitch(StmtResult &Result, EvalInfo &Info,
                                   const SwitchStmt *SS) {
BlockScopeRAII Scope(Info);

// Evaluate the switch condition.
APSInt Value;
{
  if (const Stmt *Init = SS->getInit()) {
    EvalStmtResult ESR = EvaluateStmt(Result, Info, Init);
    if (ESR != ESR_Succeeded) {
      if (ESR != ESR_Failed && !Scope.destroy())
        ESR = ESR_Failed;
      return ESR;
    }
  }

  FullExpressionRAII CondScope(Info);
  if (SS->getConditionVariable() &&
      !EvaluateDecl(Info, SS->getConditionVariable()))
    return ESR_Failed;
  if (!EvaluateInteger(SS->getCond(), Value, Info))
    return ESR_Failed;
  if (!CondScope.destroy())
    return ESR_Failed;
}

// Find the switch case corresponding to the value of the condition.
// FIXME: Cache this lookup.
const SwitchCase *Found = nullptr;
for (const SwitchCase *SC = SS->getSwitchCaseList(); SC;
     SC = SC->getNextSwitchCase()) {
  if (isa<DefaultStmt>(SC)) {
    Found = SC;
    continue;
  }

  const CaseStmt *CS = cast<CaseStmt>(SC);
  APSInt LHS = CS->getLHS()->EvaluateKnownConstInt(Info.Ctx);
  APSInt RHS = CS->getRHS() ? CS->getRHS()->EvaluateKnownConstInt(Info.Ctx)
                            : LHS;
  if (LHS <= Value && Value <= RHS) {
    Found = SC;
    break;
  }
}

if (!Found)
  return Scope.destroy() ? ESR_Succeeded : ESR_Failed;

// Search the switch body for the switch case and evaluate it from there.
EvalStmtResult ESR = EvaluateStmt(Result, Info, SS->getBody(), Found);
if (ESR != ESR_Failed && ESR != ESR_CaseNotFound && !Scope.destroy())
  return ESR_Failed;

switch (ESR) {
case ESR_Break:
  return ESR_Succeeded;
case ESR_Succeeded:
case ESR_Continue:
case ESR_Failed:
case ESR_Returned:
  return ESR;
case ESR_CaseNotFound:
  // This can only happen if the switch case is nested within a statement
  // expression. We have no intention of supporting that.
  Info.FFDiag(Found->getBeginLoc(),
              diag::note_constexpr_stmt_expr_unsupported);
  return ESR_Failed;
}
llvm_unreachable("Invalid EvalStmtResult!")__builtin_unreachable();
4982}

4984// Evaluate a statement.
4985static EvalStmtResult EvaluateStmt(StmtResult &Result, EvalInfo &Info,
                                 const Stmt *S, const SwitchCase *Case) {
if (!Info.nextStep(S))
  return ESR_Failed;

// If we're hunting down a 'case' or 'default' label, recurse through
// substatements until we hit the label.
if (Case) {
  switch (S->getStmtClass()) {
  case Stmt::CompoundStmtClass:
    // FIXME: Precompute which substatement of a compound statement we
    // would jump to, and go straight there rather than performing a
    // linear scan each time.
  case Stmt::LabelStmtClass:
  case Stmt::AttributedStmtClass:
  case Stmt::DoStmtClass:
    break;

  case Stmt::CaseStmtClass:
  case Stmt::DefaultStmtClass:
    if (Case == S)
      Case = nullptr;
    break;

  case Stmt::IfStmtClass: {
    // FIXME: Precompute which side of an 'if' we would jump to, and go
    // straight there rather than scanning both sides.
    const IfStmt *IS = cast<IfStmt>(S);

    // Wrap the evaluation in a block scope, in case it's a DeclStmt
    // preceded by our switch label.
    BlockScopeRAII Scope(Info);

    // Step into the init statement in case it brings an (uninitialized)
    // variable into scope.
    if (const Stmt *Init = IS->getInit()) {
      EvalStmtResult ESR = EvaluateStmt(Result, Info, Init, Case);
      if (ESR != ESR_CaseNotFound) {
        assert(ESR != ESR_Succeeded)((void)0);
        return ESR;
      }
    }

    // Condition variable must be initialized if it exists.
    // FIXME: We can skip evaluating the body if there's a condition
    // variable, as there can't be any case labels within it.
    // (The same is true for 'for' statements.)

    EvalStmtResult ESR = EvaluateStmt(Result, Info, IS->getThen(), Case);
    if (ESR == ESR_Failed)
      return ESR;
    if (ESR != ESR_CaseNotFound)
      return Scope.destroy() ? ESR : ESR_Failed;
    if (!IS->getElse())
      return ESR_CaseNotFound;

    ESR = EvaluateStmt(Result, Info, IS->getElse(), Case);
    if (ESR == ESR_Failed)
      return ESR;
    if (ESR != ESR_CaseNotFound)
      return Scope.destroy() ? ESR : ESR_Failed;
    return ESR_CaseNotFound;
  }

  case Stmt::WhileStmtClass: {
    EvalStmtResult ESR =
        EvaluateLoopBody(Result, Info, cast<WhileStmt>(S)->getBody(), Case);
    if (ESR != ESR_Continue)
      return ESR;
    break;
  }

  case Stmt::ForStmtClass: {
    const ForStmt *FS = cast<ForStmt>(S);
    BlockScopeRAII Scope(Info);

    // Step into the init statement in case it brings an (uninitialized)
    // variable into scope.
    if (const Stmt *Init = FS->getInit()) {
      EvalStmtResult ESR = EvaluateStmt(Result, Info, Init, Case);
      if (ESR != ESR_CaseNotFound) {
        assert(ESR != ESR_Succeeded)((void)0);
        return ESR;
      }
    }

    EvalStmtResult ESR =
        EvaluateLoopBody(Result, Info, FS->getBody(), Case);
    if (ESR != ESR_Continue)
      return ESR;
    if (const auto *Inc = FS->getInc()) {
      if (Inc->isValueDependent()) {
        if (!EvaluateDependentExpr(Inc, Info))
          return ESR_Failed;
      } else {
        FullExpressionRAII IncScope(Info);
        if (!EvaluateIgnoredValue(Info, Inc) || !IncScope.destroy())
          return ESR_Failed;
      }
    }
    break;
  }

  case Stmt::DeclStmtClass: {
    // Start the lifetime of any uninitialized variables we encounter. They
    // might be used by the selected branch of the switch.
    const DeclStmt *DS = cast<DeclStmt>(S);
    for (const auto *D : DS->decls()) {
      if (const auto *VD = dyn_cast<VarDecl>(D)) {
        if (VD->hasLocalStorage() && !VD->getInit())
          if (!EvaluateVarDecl(Info, VD))
            return ESR_Failed;
        // FIXME: If the variable has initialization that can't be jumped
        // over, bail out of any immediately-surrounding compound-statement
        // too. There can't be any case labels here.
      }
    }
    return ESR_CaseNotFound;
  }

  default:
    return ESR_CaseNotFound;
  }
}

switch (S->getStmtClass()) {
default:
  if (const Expr *E = dyn_cast<Expr>(S)) {
    if (E->isValueDependent()) {
      if (!EvaluateDependentExpr(E, Info))
        return ESR_Failed;
    } else {
      // Don't bother evaluating beyond an expression-statement which couldn't
      // be evaluated.
      // FIXME: Do we need the FullExpressionRAII object here?
      // VisitExprWithCleanups should create one when necessary.
      FullExpressionRAII Scope(Info);
      if (!EvaluateIgnoredValue(Info, E) || !Scope.destroy())
        return ESR_Failed;
    }
    return ESR_Succeeded;
  }

  Info.FFDiag(S->getBeginLoc());
  return ESR_Failed;

case Stmt::NullStmtClass:
  return ESR_Succeeded;

case Stmt::DeclStmtClass: {
  const DeclStmt *DS = cast<DeclStmt>(S);
  for (const auto *D : DS->decls()) {
    // Each declaration initialization is its own full-expression.
    FullExpressionRAII Scope(Info);
    if (!EvaluateDecl(Info, D) && !Info.noteFailure())
      return ESR_Failed;
    if (!Scope.destroy())
      return ESR_Failed;
  }
  return ESR_Succeeded;
}

case Stmt::ReturnStmtClass: {
  const Expr *RetExpr = cast<ReturnStmt>(S)->getRetValue();
  FullExpressionRAII Scope(Info);
  if (RetExpr && RetExpr->isValueDependent()) {
    EvaluateDependentExpr(RetExpr, Info);
    // We know we returned, but we don't know what the value is.
    return ESR_Failed;
  }
  if (RetExpr &&
      !(Result.Slot
            ? EvaluateInPlace(Result.Value, Info, *Result.Slot, RetExpr)
            : Evaluate(Result.Value, Info, RetExpr)))
    return ESR_Failed;
  return Scope.destroy() ? ESR_Returned : ESR_Failed;
}

case Stmt::CompoundStmtClass: {
  BlockScopeRAII Scope(Info);

  const CompoundStmt *CS = cast<CompoundStmt>(S);
  for (const auto *BI : CS->body()) {
    EvalStmtResult ESR = EvaluateStmt(Result, Info, BI, Case);
    if (ESR == ESR_Succeeded)
      Case = nullptr;
    else if (ESR != ESR_CaseNotFound) {
      if (ESR != ESR_Failed && !Scope.destroy())
        return ESR_Failed;
      return ESR;
    }
  }
  if (Case)
    return ESR_CaseNotFound;
  return Scope.destroy() ? ESR_Succeeded : ESR_Failed;
}

case Stmt::IfStmtClass: {
  const IfStmt *IS = cast<IfStmt>(S);

  // Evaluate the condition, as either a var decl or as an expression.
  BlockScopeRAII Scope(Info);
  if (const Stmt *Init = IS->getInit()) {
    EvalStmtResult ESR = EvaluateStmt(Result, Info, Init);
    if (ESR != ESR_Succeeded) {
      if (ESR != ESR_Failed && !Scope.destroy())
        return ESR_Failed;
      return ESR;
    }
  }
  bool Cond;
  if (!EvaluateCond(Info, IS->getConditionVariable(), IS->getCond(), Cond))
    return ESR_Failed;

  if (const Stmt *SubStmt = Cond ? IS->getThen() : IS->getElse()) {
    EvalStmtResult ESR = EvaluateStmt(Result, Info, SubStmt);
    if (ESR != ESR_Succeeded) {
      if (ESR != ESR_Failed && !Scope.destroy())
        return ESR_Failed;
      return ESR;
    }
  }
  return Scope.destroy() ? ESR_Succeeded : ESR_Failed;
}

case Stmt::WhileStmtClass: {
  const WhileStmt *WS = cast<WhileStmt>(S);
  while (true) {
    BlockScopeRAII Scope(Info);
    bool Continue;
    if (!EvaluateCond(Info, WS->getConditionVariable(), WS->getCond(),
                      Continue))
      return ESR_Failed;
    if (!Continue)
      break;

    EvalStmtResult ESR = EvaluateLoopBody(Result, Info, WS->getBody());
    if (ESR != ESR_Continue) {
      if (ESR != ESR_Failed && !Scope.destroy())
        return ESR_Failed;
      return ESR;
    }
    if (!Scope.destroy())
      return ESR_Failed;
  }
  return ESR_Succeeded;
}

case Stmt::DoStmtClass: {
  const DoStmt *DS = cast<DoStmt>(S);
  bool Continue;
  do {
    EvalStmtResult ESR = EvaluateLoopBody(Result, Info, DS->getBody(), Case);
    if (ESR != ESR_Continue)
      return ESR;
    Case = nullptr;

    if (DS->getCond()->isValueDependent()) {
      EvaluateDependentExpr(DS->getCond(), Info);
      // Bailout as we don't know whether to keep going or terminate the loop.
      return ESR_Failed;
    }
    FullExpressionRAII CondScope(Info);
    if (!EvaluateAsBooleanCondition(DS->getCond(), Continue, Info) ||
        !CondScope.destroy())
      return ESR_Failed;
  } while (Continue);
  return ESR_Succeeded;
}

case Stmt::ForStmtClass: {
  const ForStmt *FS = cast<ForStmt>(S);
  BlockScopeRAII ForScope(Info);
  if (FS->getInit()) {
    EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getInit());
    if (ESR != ESR_Succeeded) {
      if (ESR != ESR_Failed && !ForScope.destroy())
        return ESR_Failed;
      return ESR;
    }
  }
  while (true) {
    BlockScopeRAII IterScope(Info);
    bool Continue = true;
    if (FS->getCond() && !EvaluateCond(Info, FS->getConditionVariable(),
                                       FS->getCond(), Continue))
      return ESR_Failed;
    if (!Continue)
      break;

    EvalStmtResult ESR = EvaluateLoopBody(Result, Info, FS->getBody());
    if (ESR != ESR_Continue) {
      if (ESR != ESR_Failed && (!IterScope.destroy() || !ForScope.destroy()))
        return ESR_Failed;
      return ESR;
    }

    if (const auto *Inc = FS->getInc()) {
      if (Inc->isValueDependent()) {
        if (!EvaluateDependentExpr(Inc, Info))
          return ESR_Failed;
      } else {
        FullExpressionRAII IncScope(Info);
        if (!EvaluateIgnoredValue(Info, Inc) || !IncScope.destroy())
          return ESR_Failed;
      }
    }

    if (!IterScope.destroy())
      return ESR_Failed;
  }
  return ForScope.destroy() ? ESR_Succeeded : ESR_Failed;
}

case Stmt::CXXForRangeStmtClass: {
  const CXXForRangeStmt *FS = cast<CXXForRangeStmt>(S);
  BlockScopeRAII Scope(Info);

  // Evaluate the init-statement if present.
  if (FS->getInit()) {
    EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getInit());
    if (ESR != ESR_Succeeded) {
      if (ESR != ESR_Failed && !Scope.destroy())
        return ESR_Failed;
      return ESR;
    }
  }

  // Initialize the __range variable.
  EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getRangeStmt());
  if (ESR != ESR_Succeeded) {
    if (ESR != ESR_Failed && !Scope.destroy())
      return ESR_Failed;
    return ESR;
  }

  // Create the __begin and __end iterators.
  ESR = EvaluateStmt(Result, Info, FS->getBeginStmt());
  if (ESR != ESR_Succeeded) {
    if (ESR != ESR_Failed && !Scope.destroy())
      return ESR_Failed;
    return ESR;
  }
  ESR = EvaluateStmt(Result, Info, FS->getEndStmt());
  if (ESR != ESR_Succeeded) {
    if (ESR != ESR_Failed && !Scope.destroy())
      return ESR_Failed;
    return ESR;
  }

  while (true) {
    // Condition: __begin != __end.
    {
      if (FS->getCond()->isValueDependent()) {
        EvaluateDependentExpr(FS->getCond(), Info);
        // We don't know whether to keep going or terminate the loop.
        return ESR_Failed;
      }
      bool Continue = true;
      FullExpressionRAII CondExpr(Info);
      if (!EvaluateAsBooleanCondition(FS->getCond(), Continue, Info))
        return ESR_Failed;
      if (!Continue)
        break;
    }

    // User's variable declaration, initialized by *__begin.
    BlockScopeRAII InnerScope(Info);
    ESR = EvaluateStmt(Result, Info, FS->getLoopVarStmt());
    if (ESR != ESR_Succeeded) {
      if (ESR != ESR_Failed && (!InnerScope.destroy() || !Scope.destroy()))
        return ESR_Failed;
      return ESR;
    }

    // Loop body.
    ESR = EvaluateLoopBody(Result, Info, FS->getBody());
    if (ESR != ESR_Continue) {
      if (ESR != ESR_Failed && (!InnerScope.destroy() || !Scope.destroy()))
        return ESR_Failed;
      return ESR;
    }
    if (FS->getInc()->isValueDependent()) {
      if (!EvaluateDependentExpr(FS->getInc(), Info))
        return ESR_Failed;
    } else {
      // Increment: ++__begin
      if (!EvaluateIgnoredValue(Info, FS->getInc()))
        return ESR_Failed;
    }

    if (!InnerScope.destroy())
      return ESR_Failed;
  }

  return Scope.destroy() ? ESR_Succeeded : ESR_Failed;
}

case Stmt::SwitchStmtClass:
  return EvaluateSwitch(Result, Info, cast<SwitchStmt>(S));

case Stmt::ContinueStmtClass:
  return ESR_Continue;

case Stmt::BreakStmtClass:
  return ESR_Break;

case Stmt::LabelStmtClass:
  return EvaluateStmt(Result, Info, cast<LabelStmt>(S)->getSubStmt(), Case);

case Stmt::AttributedStmtClass:
  // As a general principle, C++11 attributes can be ignored without
  // any semantic impact.
  return EvaluateStmt(Result, Info, cast<AttributedStmt>(S)->getSubStmt(),
                      Case);

case Stmt::CaseStmtClass:
case Stmt::DefaultStmtClass:
  return EvaluateStmt(Result, Info, cast<SwitchCase>(S)->getSubStmt(), Case);
case Stmt::CXXTryStmtClass:
  // Evaluate try blocks by evaluating all sub statements.
  return EvaluateStmt(Result, Info, cast<CXXTryStmt>(S)->getTryBlock(), Case);
}
5408}

5410/// CheckTrivialDefaultConstructor - Check whether a constructor is a trivial
5411/// default constructor. If so, we'll fold it whether or not it's marked as
5412/// constexpr. If it is marked as constexpr, we will never implicitly define it,
5413/// so we need special handling.
5414static bool CheckTrivialDefaultConstructor(EvalInfo &Info, SourceLocation Loc,
                                         const CXXConstructorDecl *CD,
                                         bool IsValueInitialization) {
if (!CD->isTrivial() || !CD->isDefaultConstructor())
  return false;

// Value-initialization does not call a trivial default constructor, so such a
// call is a core constant expression whether or not the constructor is
// constexpr.
if (!CD->isConstexpr() && !IsValueInitialization) {
  if (Info.getLangOpts().CPlusPlus11) {
    // FIXME: If DiagDecl is an implicitly-declared special member function,
    // we should be much more explicit about why it's not constexpr.
    Info.CCEDiag(Loc, diag::note_constexpr_invalid_function, 1)
      << /*IsConstexpr*/0 << /*IsConstructor*/1 << CD;
    Info.Note(CD->getLocation(), diag::note_declared_at);
  } else {
    Info.CCEDiag(Loc, diag::note_invalid_subexpr_in_const_expr);
  }
}
return true;
5435}

5437/// CheckConstexprFunction - Check that a function can be called in a constant
5438/// expression.
5439static bool CheckConstexprFunction(EvalInfo &Info, SourceLocation CallLoc,
                                 const FunctionDecl *Declaration,
                                 const FunctionDecl *Definition,
                                 const Stmt *Body) {
// Potential constant expressions can contain calls to declared, but not yet
// defined, constexpr functions.
if (Info.checkingPotentialConstantExpression() && !Definition &&
    Declaration->isConstexpr())
  return false;

// Bail out if the function declaration itself is invalid.  We will
// have produced a relevant diagnostic while parsing it, so just
// note the problematic sub-expression.
if (Declaration->isInvalidDecl()) {
  Info.FFDiag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
  return false;
}

// DR1872: An instantiated virtual constexpr function can't be called in a
// constant expression (prior to C++20). We can still constant-fold such a
// call.
if (!Info.Ctx.getLangOpts().CPlusPlus20 && isa<CXXMethodDecl>(Declaration) &&
    cast<CXXMethodDecl>(Declaration)->isVirtual())
  Info.CCEDiag(CallLoc, diag::note_constexpr_virtual_call);

if (Definition && Definition->isInvalidDecl()) {
  Info.FFDiag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
  return false;
}

// Can we evaluate this function call?
if (Definition && Definition->isConstexpr() && Body)
  return true;

if (Info.getLangOpts().CPlusPlus11) {
  const FunctionDecl *DiagDecl = Definition ? Definition : Declaration;

  // If this function is not constexpr because it is an inherited
  // non-constexpr constructor, diagnose that directly.
  auto *CD = dyn_cast<CXXConstructorDecl>(DiagDecl);
  if (CD && CD->isInheritingConstructor()) {
    auto *Inherited = CD->getInheritedConstructor().getConstructor();
    if (!Inherited->isConstexpr())
      DiagDecl = CD = Inherited;
  }

  // FIXME: If DiagDecl is an implicitly-declared special member function
  // or an inheriting constructor, we should be much more explicit about why
  // it's not constexpr.
  if (CD && CD->isInheritingConstructor())
    Info.FFDiag(CallLoc, diag::note_constexpr_invalid_inhctor, 1)
      << CD->getInheritedConstructor().getConstructor()->getParent();
  else
    Info.FFDiag(CallLoc, diag::note_constexpr_invalid_function, 1)
      << DiagDecl->isConstexpr() << (bool)CD << DiagDecl;
  Info.Note(DiagDecl->getLocation(), diag::note_declared_at);
} else {
  Info.FFDiag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
}
return false;
5499}

5501namespace {
5502struct CheckDynamicTypeHandler {
AccessKinds AccessKind;
typedef bool result_type;
bool failed() { return false; }
bool found(APValue &Subobj, QualType SubobjType) { return true; }
bool found(APSInt &Value, QualType SubobjType) { return true; }
bool found(APFloat &Value, QualType SubobjType) { return true; }
5509};
5510} // end anonymous namespace

5512/// Check that we can access the notional vptr of an object / determine its
5513/// dynamic type.
5514static bool checkDynamicType(EvalInfo &Info, const Expr *E, const LValue &This,
                           AccessKinds AK, bool Polymorphic) {
if (This.Designator.Invalid)
  return false;

CompleteObject Obj = findCompleteObject(Info, E, AK, This, QualType());

if (!Obj)
  return false;

if (!Obj.Value) {
  // The object is not usable in constant expressions, so we can't inspect
  // its value to see if it's in-lifetime or what the active union members
  // are. We can still check for a one-past-the-end lvalue.
  if (This.Designator.isOnePastTheEnd() ||
      This.Designator.isMostDerivedAnUnsizedArray()) {
    Info.FFDiag(E, This.Designator.isOnePastTheEnd()
                       ? diag::note_constexpr_access_past_end
                       : diag::note_constexpr_access_unsized_array)
        << AK;
    return false;
  } else if (Polymorphic) {
    // Conservatively refuse to perform a polymorphic operation if we would
    // not be able to read a notional 'vptr' value.
    APValue Val;
    This.moveInto(Val);
    QualType StarThisType =
        Info.Ctx.getLValueReferenceType(This.Designator.getType(Info.Ctx));
    Info.FFDiag(E, diag::note_constexpr_polymorphic_unknown_dynamic_type)
        << AK << Val.getAsString(Info.Ctx, StarThisType);
    return false;
  }
  return true;
}

CheckDynamicTypeHandler Handler{AK};
return Obj && findSubobject(Info, E, Obj, This.Designator, Handler);
5551}

5553/// Check that the pointee of the 'this' pointer in a member function call is
5554/// either within its lifetime or in its period of construction or destruction.
5555static bool
5556checkNonVirtualMemberCallThisPointer(EvalInfo &Info, const Expr *E,
                                   const LValue &This,
                                   const CXXMethodDecl *NamedMember) {
return checkDynamicType(
    Info, E, This,
    isa<CXXDestructorDecl>(NamedMember) ? AK_Destroy : AK_MemberCall, false);
5562}

5564struct DynamicType {
/// The dynamic class type of the object.
const CXXRecordDecl *Type;
/// The corresponding path length in the lvalue.
unsigned PathLength;
5569};

5571static const CXXRecordDecl *getBaseClassType(SubobjectDesignator &Designator,
                                           unsigned PathLength) {
assert(PathLength >= Designator.MostDerivedPathLength && PathLength <=((void)0)
    Designator.Entries.size() && "invalid path length")((void)0);
return (PathLength == Designator.MostDerivedPathLength)
           ? Designator.MostDerivedType->getAsCXXRecordDecl()
           : getAsBaseClass(Designator.Entries[PathLength - 1]);
5578}

5580/// Determine the dynamic type of an object.
5581static Optional<DynamicType> ComputeDynamicType(EvalInfo &Info, const Expr *E,
                                              LValue &This, AccessKinds AK) {
// If we don't have an lvalue denoting an object of class type, there is no
// meaningful dynamic type. (We consider objects of non-class type to have no
// dynamic type.)
if (!checkDynamicType(Info, E, This, AK, true))
  return None;

// Refuse to compute a dynamic type in the presence of virtual bases. This
// shouldn't happen other than in constant-folding situations, since literal
// types can't have virtual bases.
//
// Note that consumers of DynamicType assume that the type has no virtual
// bases, and will need modifications if this restriction is relaxed.
const CXXRecordDecl *Class =
    This.Designator.MostDerivedType->getAsCXXRecordDecl();
if (!Class || Class->getNumVBases()) {
  Info.FFDiag(E);
  return None;
}

// FIXME: For very deep class hierarchies, it might be beneficial to use a
// binary search here instead. But the overwhelmingly common case is that
// we're not in the middle of a constructor, so it probably doesn't matter
// in practice.
ArrayRef<APValue::LValuePathEntry> Path = This.Designator.Entries;
for (unsigned PathLength = This.Designator.MostDerivedPathLength;
     PathLength <= Path.size(); ++PathLength) {
  switch (Info.isEvaluatingCtorDtor(This.getLValueBase(),
                                    Path.slice(0, PathLength))) {
  case ConstructionPhase::Bases:
  case ConstructionPhase::DestroyingBases:
    // We're constructing or destroying a base class. This is not the dynamic
    // type.
    break;

  case ConstructionPhase::None:
  case ConstructionPhase::AfterBases:
  case ConstructionPhase::AfterFields:
  case ConstructionPhase::Destroying:
    // We've finished constructing the base classes and not yet started
    // destroying them again, so this is the dynamic type.
    return DynamicType{getBaseClassType(This.Designator, PathLength),
                       PathLength};
  }
}

// CWG issue 1517: we're constructing a base class of the object described by
// 'This', so that object has not yet begun its period of construction and
// any polymorphic operation on it results in undefined behavior.
Info.FFDiag(E);
return None;
5633}

5635/// Perform virtual dispatch.
5636static const CXXMethodDecl *HandleVirtualDispatch(
  EvalInfo &Info, const Expr *E, LValue &This, const CXXMethodDecl *Found,
  llvm::SmallVectorImpl<QualType> &CovariantAdjustmentPath) {
Optional<DynamicType> DynType = ComputeDynamicType(
    Info, E, This,
    isa<CXXDestructorDecl>(Found) ? AK_Destroy : AK_MemberCall);
if (!DynType)
  return nullptr;

// Find the final overrider. It must be declared in one of the classes on the
// path from the dynamic type to the static type.
// FIXME: If we ever allow literal types to have virtual base classes, that
// won't be true.
const CXXMethodDecl *Callee = Found;
unsigned PathLength = DynType->PathLength;
for (/**/; PathLength <= This.Designator.Entries.size(); ++PathLength) {
  const CXXRecordDecl *Class = getBaseClassType(This.Designator, PathLength);
  const CXXMethodDecl *Overrider =
      Found->getCorrespondingMethodDeclaredInClass(Class, false);
  if (Overrider) {
    Callee = Overrider;
    break;
  }
}

// C++2a [class.abstract]p6:
//   the effect of making a virtual call to a pure virtual function [...] is
//   undefined
if (Callee->isPure()) {
  Info.FFDiag(E, diag::note_constexpr_pure_virtual_call, 1) << Callee;
  Info.Note(Callee->getLocation(), diag::note_declared_at);
  return nullptr;
}

// If necessary, walk the rest of the path to determine the sequence of
// covariant adjustment steps to apply.
if (!Info.Ctx.hasSameUnqualifiedType(Callee->getReturnType(),
                                     Found->getReturnType())) {
  CovariantAdjustmentPath.push_back(Callee->getReturnType());
  for (unsigned CovariantPathLength = PathLength + 1;
       CovariantPathLength != This.Designator.Entries.size();
       ++CovariantPathLength) {
    const CXXRecordDecl *NextClass =
        getBaseClassType(This.Designator, CovariantPathLength);
    const CXXMethodDecl *Next =
        Found->getCorrespondingMethodDeclaredInClass(NextClass, false);
    if (Next && !Info.Ctx.hasSameUnqualifiedType(
                    Next->getReturnType(), CovariantAdjustmentPath.back()))
      CovariantAdjustmentPath.push_back(Next->getReturnType());
  }
  if (!Info.Ctx.hasSameUnqualifiedType(Found->getReturnType(),
                                       CovariantAdjustmentPath.back()))
    CovariantAdjustmentPath.push_back(Found->getReturnType());
}

// Perform 'this' adjustment.
if (!CastToDerivedClass(Info, E, This, Callee->getParent(), PathLength))
  return nullptr;

return Callee;
5696}

5698/// Perform the adjustment from a value returned by a virtual function to
5699/// a value of the statically expected type, which may be a pointer or
5700/// reference to a base class of the returned type.
5701static bool HandleCovariantReturnAdjustment(EvalInfo &Info, const Expr *E,
                                          APValue &Result,
                                          ArrayRef<QualType> Path) {
assert(Result.isLValue() &&((void)0)
       "unexpected kind of APValue for covariant return")((void)0);
if (Result.isNullPointer())
  return true;

LValue LVal;
LVal.setFrom(Info.Ctx, Result);

const CXXRecordDecl *OldClass = Path[0]->getPointeeCXXRecordDecl();
for (unsigned I = 1; I != Path.size(); ++I) {
  const CXXRecordDecl *NewClass = Path[I]->getPointeeCXXRecordDecl();
  assert(OldClass && NewClass && "unexpected kind of covariant return")((void)0);
  if (OldClass != NewClass &&
      !CastToBaseClass(Info, E, LVal, OldClass, NewClass))
    return false;
  OldClass = NewClass;
}

LVal.moveInto(Result);
return true;
5724}

5726/// Determine whether \p Base, which is known to be a direct base class of
5727/// \p Derived, is a public base class.
5728static bool isBaseClassPublic(const CXXRecordDecl *Derived,
                            const CXXRecordDecl *Base) {
for (const CXXBaseSpecifier &BaseSpec : Derived->bases()) {
  auto *BaseClass = BaseSpec.getType()->getAsCXXRecordDecl();
  if (BaseClass && declaresSameEntity(BaseClass, Base))
    return BaseSpec.getAccessSpecifier() == AS_public;
}
llvm_unreachable("Base is not a direct base of Derived")__builtin_unreachable();
5736}

5738/// Apply the given dynamic cast operation on the provided lvalue.
5739///
5740/// This implements the hard case of dynamic_cast, requiring a "runtime check"
5741/// to find a suitable target subobject.
5742static bool HandleDynamicCast(EvalInfo &Info, const ExplicitCastExpr *E,
                            LValue &Ptr) {
// We can't do anything with a non-symbolic pointer value.
SubobjectDesignator &D = Ptr.Designator;
if (D.Invalid)
  return false;

// C++ [expr.dynamic.cast]p6:
//   If v is a null pointer value, the result is a null pointer value.
if (Ptr.isNullPointer() && !E->isGLValue())
  return true;

// For all the other cases, we need the pointer to point to an object within
// its lifetime / period of construction / destruction, and we need to know
// its dynamic type.
Optional<DynamicType> DynType =
    ComputeDynamicType(Info, E, Ptr, AK_DynamicCast);
if (!DynType)
  return false;

// C++ [expr.dynamic.cast]p7:
//   If T is "pointer to cv void", then the result is a pointer to the most
//   derived object
if (E->getType()->isVoidPointerType())
  return CastToDerivedClass(Info, E, Ptr, DynType->Type, DynType->PathLength);

const CXXRecordDecl *C = E->getTypeAsWritten()->getPointeeCXXRecordDecl();
assert(C && "dynamic_cast target is not void pointer nor class")((void)0);
CanQualType CQT = Info.Ctx.getCanonicalType(Info.Ctx.getRecordType(C));

auto RuntimeCheckFailed = [&] (CXXBasePaths *Paths) {
  // C++ [expr.dynamic.cast]p9:
  if (!E->isGLValue()) {
    //   The value of a failed cast to pointer type is the null pointer value
    //   of the required result type.
    Ptr.setNull(Info.Ctx, E->getType());
    return true;
  }

  //   A failed cast to reference type throws [...] std::bad_cast.
  unsigned DiagKind;
  if (!Paths && (declaresSameEntity(DynType->Type, C) ||
                 DynType->Type->isDerivedFrom(C)))
    DiagKind = 0;
  else if (!Paths || Paths->begin() == Paths->end())
    DiagKind = 1;
  else if (Paths->isAmbiguous(CQT))
    DiagKind = 2;
  else {
    assert(Paths->front().Access != AS_public && "why did the cast fail?")((void)0);
    DiagKind = 3;
  }
  Info.FFDiag(E, diag::note_constexpr_dynamic_cast_to_reference_failed)
      << DiagKind << Ptr.Designator.getType(Info.Ctx)
      << Info.Ctx.getRecordType(DynType->Type)
      << E->getType().getUnqualifiedType();
  return false;
};

// Runtime check, phase 1:
//   Walk from the base subobject towards the derived object looking for the
//   target type.
for (int PathLength = Ptr.Designator.Entries.size();
     PathLength >= (int)DynType->PathLength; --PathLength) {
  const CXXRecordDecl *Class = getBaseClassType(Ptr.Designator, PathLength);
  if (declaresSameEntity(Class, C))
    return CastToDerivedClass(Info, E, Ptr, Class, PathLength);
  // We can only walk across public inheritance edges.
  if (PathLength > (int)DynType->PathLength &&
      !isBaseClassPublic(getBaseClassType(Ptr.Designator, PathLength - 1),
                         Class))
    return RuntimeCheckFailed(nullptr);
}

// Runtime check, phase 2:
//   Search the dynamic type for an unambiguous public base of type C.
CXXBasePaths Paths(/*FindAmbiguities=*/true,
                   /*RecordPaths=*/true, /*DetectVirtual=*/false);
if (DynType->Type->isDerivedFrom(C, Paths) && !Paths.isAmbiguous(CQT) &&
    Paths.front().Access == AS_public) {
  // Downcast to the dynamic type...
  if (!CastToDerivedClass(Info, E, Ptr, DynType->Type, DynType->PathLength))
    return false;
  // ... then upcast to the chosen base class subobject.
  for (CXXBasePathElement &Elem : Paths.front())
    if (!HandleLValueBase(Info, E, Ptr, Elem.Class, Elem.Base))
      return false;
  return true;
}

// Otherwise, the runtime check fails.
return RuntimeCheckFailed(&Paths);
5834}

5836namespace {
5837struct StartLifetimeOfUnionMemberHandler {
EvalInfo &Info;
const Expr *LHSExpr;
const FieldDecl *Field;
bool DuringInit;
bool Failed = false;
static const AccessKinds AccessKind = AK_Assign;

typedef bool result_type;
bool failed() { return Failed; }
bool found(APValue &Subobj, QualType SubobjType) {
  // We are supposed to perform no initialization but begin the lifetime of
  // the object. We interpret that as meaning to do what default
  // initialization of the object would do if all constructors involved were
  // trivial:
  //  * All base, non-variant member, and array element subobjects' lifetimes
  //    begin
  //  * No variant members' lifetimes begin
  //  * All scalar subobjects whose lifetimes begin have indeterminate values
  assert(SubobjType->isUnionType())((void)0);
  if (declaresSameEntity(Subobj.getUnionField(), Field)) {
    // This union member is already active. If it's also in-lifetime, there's
    // nothing to do.
    if (Subobj.getUnionValue().hasValue())
      return true;
  } else if (DuringInit) {
    // We're currently in the process of initializing a different union
    // member.  If we carried on, that initialization would attempt to
    // store to an inactive union member, resulting in undefined behavior.
    Info.FFDiag(LHSExpr,
                diag::note_constexpr_union_member_change_during_init);
    return false;
  }
  APValue Result;
  Failed = !getDefaultInitValue(Field->getType(), Result);
  Subobj.setUnion(Field, Result);
  return true;
}
bool found(APSInt &Value, QualType SubobjType) {
  llvm_unreachable("wrong value kind for union object")__builtin_unreachable();
}
bool found(APFloat &Value, QualType SubobjType) {
  llvm_unreachable("wrong value kind for union object")__builtin_unreachable();
}
5881};
5882} // end anonymous namespace

5884const AccessKinds StartLifetimeOfUnionMemberHandler::AccessKind;

5886/// Handle a builtin simple-assignment or a call to a trivial assignment
5887/// operator whose left-hand side might involve a union member access. If it
5888/// does, implicitly start the lifetime of any accessed union elements per
5889/// C++20 [class.union]5.
5890static bool HandleUnionActiveMemberChange(EvalInfo &Info, const Expr *LHSExpr,
                                        const LValue &LHS) {
if (LHS.InvalidBase || LHS.Designator.Invalid)
92
←
Assuming field 'InvalidBase' is false→
93
←
Assuming field 'Invalid' is 0→
94
←
Taking false branch→
  return false;

llvm::SmallVector<std::pair<unsigned, const FieldDecl*>, 4> UnionPathLengths;
// C++ [class.union]p5:
//   define the set S(E) of subexpressions of E as follows:
unsigned PathLength = LHS.Designator.Entries.size();
for (const Expr *E = LHSExpr; E != nullptr;) {
95
←
Assuming pointer value is null→
96
←
Loop condition is false. Execution continues on line 5960→
  //   -- If E is of the form A.B, S(E) contains the elements of S(A)...
  if (auto *ME = dyn_cast<MemberExpr>(E)) {
    auto *FD = dyn_cast<FieldDecl>(ME->getMemberDecl());
    // Note that we can't implicitly start the lifetime of a reference,
    // so we don't need to proceed any further if we reach one.
    if (!FD || FD->getType()->isReferenceType())
      break;

    //    ... and also contains A.B if B names a union member ...
    if (FD->getParent()->isUnion()) {
      //    ... of a non-class, non-array type, or of a class type with a
      //    trivial default constructor that is not deleted, or an array of
      //    such types.
      auto *RD =
          FD->getType()->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
      if (!RD || RD->hasTrivialDefaultConstructor())
        UnionPathLengths.push_back({PathLength - 1, FD});
    }

    E = ME->getBase();
    --PathLength;
    assert(declaresSameEntity(FD,((void)0)
                              LHS.Designator.Entries[PathLength]((void)0)
                                  .getAsBaseOrMember().getPointer()))((void)0);

    //   -- If E is of the form A[B] and is interpreted as a built-in array
    //      subscripting operator, S(E) is [S(the array operand, if any)].
  } else if (auto *ASE = dyn_cast<ArraySubscriptExpr>(E)) {
    // Step over an ArrayToPointerDecay implicit cast.
    auto *Base = ASE->getBase()->IgnoreImplicit();
    if (!Base->getType()->isArrayType())
      break;

    E = Base;
    --PathLength;

  } else if (auto *ICE = dyn_cast<ImplicitCastExpr>(E)) {
    // Step over a derived-to-base conversion.
    E = ICE->getSubExpr();
    if (ICE->getCastKind() == CK_NoOp)
      continue;
    if (ICE->getCastKind() != CK_DerivedToBase &&
        ICE->getCastKind() != CK_UncheckedDerivedToBase)
      break;
    // Walk path backwards as we walk up from the base to the derived class.
    for (const CXXBaseSpecifier *Elt : llvm::reverse(ICE->path())) {
      --PathLength;
      (void)Elt;
      assert(declaresSameEntity(Elt->getType()->getAsCXXRecordDecl(),((void)0)
                                LHS.Designator.Entries[PathLength]((void)0)
                                    .getAsBaseOrMember().getPointer()))((void)0);
    }

  //   -- Otherwise, S(E) is empty.
  } else {
    break;
  }
}

// Common case: no unions' lifetimes are started.
if (UnionPathLengths.empty())
97
←
Calling 'SmallVectorBase::empty'→
100
←
Returning from 'SmallVectorBase::empty'→
101
←
Taking false branch→
  return true;

//   if modification of X [would access an inactive union member], an object
//   of the type of X is implicitly created
CompleteObject Obj =
    findCompleteObject(Info, LHSExpr, AK_Assign, LHS, LHSExpr->getType());
102
←
Called C++ object pointer is null