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//===-- llvm/GlobalValue.h - Class to represent a global value --*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This file is a common base class of all globally definable objects.  As such,

// it is subclassed by GlobalVariable, GlobalAlias and by Function.  This is

// used because you can do certain things with these global objects that you

// can't do to anything else.  For example, use the address of one as a

// constant.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_IR_GLOBALVALUE_H

#define LLVM_IR_GLOBALVALUE_H

#include "llvm/ADT/StringRef.h"

#include "llvm/ADT/Twine.h"

#include "llvm/IR/Constant.h"

#include "llvm/IR/DerivedTypes.h"

#include "llvm/IR/Value.h"

#include "llvm/Support/Casting.h"

#include "llvm/Support/ErrorHandling.h"

#include "llvm/Support/MD5.h"

#include <cassert>

#include <cstdint>

#include <string>

namespace llvm {

class Comdat;

class ConstantRange;

class Error;

class GlobalObject;

class Module;

namespace Intrinsic {

typedef unsigned ID;

} // end namespace Intrinsic

class GlobalValue : public Constant {

public:

  /// An enumeration for the kinds of linkage for global values.

  enum LinkageTypes {

    ExternalLinkage = 0,///< Externally visible function

    AvailableExternallyLinkage, ///< Available for inspection, not emission.

    LinkOnceAnyLinkage, ///< Keep one copy of function when linking (inline)

    LinkOnceODRLinkage, ///< Same, but only replaced by something equivalent.

    WeakAnyLinkage,     ///< Keep one copy of named function when linking (weak)

    WeakODRLinkage,     ///< Same, but only replaced by something equivalent.

    AppendingLinkage,   ///< Special purpose, only applies to global arrays

    InternalLinkage,    ///< Rename collisions when linking (static functions).

    PrivateLinkage,     ///< Like Internal, but omit from symbol table.

    ExternalWeakLinkage,///< ExternalWeak linkage description.

    CommonLinkage       ///< Tentative definitions.

  };

  /// An enumeration for the kinds of visibility of global values.

  enum VisibilityTypes {

    DefaultVisibility = 0,  ///< The GV is visible

    HiddenVisibility,       ///< The GV is hidden

    ProtectedVisibility     ///< The GV is protected

  };

  /// Storage classes of global values for PE targets.

  enum DLLStorageClassTypes {

    DefaultStorageClass   = 0,

    DLLImportStorageClass = 1, ///< Function to be imported from DLL

    DLLExportStorageClass = 2  ///< Function to be accessible from DLL.

  };

protected:

  GlobalValue(Type *Ty, ValueTy VTy, Use *Ops, unsigned NumOps,

              LinkageTypes Linkage, const Twine &Name, unsigned AddressSpace)

      : Constant(PointerType::get(Ty, AddressSpace), VTy, Ops, NumOps),

        ValueType(Ty), Visibility(DefaultVisibility),

        UnnamedAddrVal(unsigned(UnnamedAddr::None)),

        DllStorageClass(DefaultStorageClass), ThreadLocal(NotThreadLocal),

        HasLLVMReservedName(false), IsDSOLocal(false), HasPartition(false),

        HasSanitizerMetadata(false) {

    setLinkage(Linkage);

    setName(Name);

  }

  Type *ValueType;

  static const unsigned GlobalValueSubClassDataBits = 15;

  // All bitfields use unsigned as the underlying type so that MSVC will pack

  // them.

  unsigned Linkage : 4;       // The linkage of this global

  unsigned Visibility : 2;    // The visibility style of this global

  unsigned UnnamedAddrVal : 2; // This value's address is not significant

  unsigned DllStorageClass : 2; // DLL storage class

  unsigned ThreadLocal : 3; // Is this symbol "Thread Local", if so, what is

                            // the desired model?

  /// True if the function's name starts with "llvm.".  This corresponds to the

  /// value of Function::isIntrinsic(), which may be true even if

  /// Function::intrinsicID() returns Intrinsic::not_intrinsic.

  unsigned HasLLVMReservedName : 1;

  /// If true then there is a definition within the same linkage unit and that

  /// definition cannot be runtime preempted.

  unsigned IsDSOLocal : 1;

  /// True if this symbol has a partition name assigned (see

  /// https://lld.llvm.org/Partitions.html).

  unsigned HasPartition : 1;

  /// True if this symbol has sanitizer metadata available. Should only happen

  /// if sanitizers were enabled when building the translation unit which

  /// contains this GV.

  unsigned HasSanitizerMetadata : 1;

private:

  // Give subclasses access to what otherwise would be wasted padding.

  // (15 + 4 + 2 + 2 + 2 + 3 + 1 + 1 + 1 + 1) == 32.

  unsigned SubClassData : GlobalValueSubClassDataBits;

  friend class Constant;

  void destroyConstantImpl();

  Value *handleOperandChangeImpl(Value *From, Value *To);

  /// Returns true if the definition of this global may be replaced by a

  /// differently optimized variant of the same source level function at link

  /// time.

  bool mayBeDerefined() const {

    switch (getLinkage()) {

    case WeakODRLinkage:

    case LinkOnceODRLinkage:

    case AvailableExternallyLinkage:

      return true;

    case WeakAnyLinkage:

    case LinkOnceAnyLinkage:

    case CommonLinkage:

    case ExternalWeakLinkage:

    case ExternalLinkage:

    case AppendingLinkage:

    case InternalLinkage:

    case PrivateLinkage:

      // Optimizations may assume builtin semantics for functions defined as

      // nobuiltin due to attributes at call-sites. To avoid applying IPO based

      // on nobuiltin semantics, treat such function definitions as maybe

      // derefined.

      return isInterposable() || isNobuiltinFnDef();

    }

    llvm_unreachable("Fully covered switch above!");

  }

  /// Returns true if the global is a function definition with the nobuiltin

  /// attribute.

  bool isNobuiltinFnDef() const;

protected:

  /// The intrinsic ID for this subclass (which must be a Function).

  ///

  /// This member is defined by this class, but not used for anything.

  /// Subclasses can use it to store their intrinsic ID, if they have one.

  ///

  /// This is stored here to save space in Function on 64-bit hosts.

  Intrinsic::ID IntID = (Intrinsic::ID)0U;

  unsigned getGlobalValueSubClassData() const {

    return SubClassData;

  }

  void setGlobalValueSubClassData(unsigned V) {

    assert(V < (1 << GlobalValueSubClassDataBits) && "It will not fit");

    SubClassData = V;

  }

  Module *Parent = nullptr; // The containing module.

  // Used by SymbolTableListTraits.

  void setParent(Module *parent) {

    Parent = parent;

  }

  ~GlobalValue() {

    removeDeadConstantUsers();   // remove any dead constants using this.

  }

public:

  enum ThreadLocalMode {

    NotThreadLocal = 0,

    GeneralDynamicTLSModel,

    LocalDynamicTLSModel,

    InitialExecTLSModel,

    LocalExecTLSModel

  };

  GlobalValue(const GlobalValue &) = delete;

  unsigned getAddressSpace() const {

    return getType()->getAddressSpace();

  }

  enum class UnnamedAddr {

    None,

    Local,

    Global,

  };

  bool hasGlobalUnnamedAddr() const {

    return getUnnamedAddr() == UnnamedAddr::Global;

  }

  /// Returns true if this value's address is not significant in this module.

  /// This attribute is intended to be used only by the code generator and LTO

  /// to allow the linker to decide whether the global needs to be in the symbol

  /// table. It should probably not be used in optimizations, as the value may

  /// have uses outside the module; use hasGlobalUnnamedAddr() instead.

  bool hasAtLeastLocalUnnamedAddr() const {

    return getUnnamedAddr() != UnnamedAddr::None;

  }

  UnnamedAddr getUnnamedAddr() const {

    return UnnamedAddr(UnnamedAddrVal);

  }

  void setUnnamedAddr(UnnamedAddr Val) { UnnamedAddrVal = unsigned(Val); }

  static UnnamedAddr getMinUnnamedAddr(UnnamedAddr A, UnnamedAddr B) {

    if (A == UnnamedAddr::None || B == UnnamedAddr::None)

      return UnnamedAddr::None;

    if (A == UnnamedAddr::Local || B == UnnamedAddr::Local)

      return UnnamedAddr::Local;

    return UnnamedAddr::Global;

  }

  bool hasComdat() const { return getComdat() != nullptr; }

  const Comdat *getComdat() const;

  Comdat *getComdat() {

    return const_cast<Comdat *>(

                           static_cast<const GlobalValue *>(this)->getComdat());

  }

  VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }

  bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; }

  bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }

  bool hasProtectedVisibility() const {

    return Visibility == ProtectedVisibility;

  }

  void setVisibility(VisibilityTypes V) {

    assert((!hasLocalLinkage() || V == DefaultVisibility) &&

           "local linkage requires default visibility");

    Visibility = V;

    if (isImplicitDSOLocal())

      setDSOLocal(true);

  }

  /// If the value is "Thread Local", its value isn't shared by the threads.

  bool isThreadLocal() const { return getThreadLocalMode() != NotThreadLocal; }

  void setThreadLocal(bool Val) {

    setThreadLocalMode(Val ? GeneralDynamicTLSModel : NotThreadLocal);

  }

  void setThreadLocalMode(ThreadLocalMode Val) {

    assert(Val == NotThreadLocal || getValueID() != Value::FunctionVal);

    ThreadLocal = Val;

  }

  ThreadLocalMode getThreadLocalMode() const {

    return static_cast<ThreadLocalMode>(ThreadLocal);

  }

  DLLStorageClassTypes getDLLStorageClass() const {

    return DLLStorageClassTypes(DllStorageClass);

  }

  bool hasDLLImportStorageClass() const {

    return DllStorageClass == DLLImportStorageClass;

  }

  bool hasDLLExportStorageClass() const {

    return DllStorageClass == DLLExportStorageClass;

  }

  void setDLLStorageClass(DLLStorageClassTypes C) {

    assert((!hasLocalLinkage() || C == DefaultStorageClass) &&

           "local linkage requires DefaultStorageClass");

    DllStorageClass = C;

  }

  bool hasSection() const { return !getSection().empty(); }

  StringRef getSection() const;

  /// Global values are always pointers.

  PointerType *getType() const { return cast<PointerType>(User::getType()); }

  Type *getValueType() const { return ValueType; }

  bool isImplicitDSOLocal() const {

    return hasLocalLinkage() ||

           (!hasDefaultVisibility() && !hasExternalWeakLinkage());

  }

  void setDSOLocal(bool Local) { IsDSOLocal = Local; }

  bool isDSOLocal() const {

    return IsDSOLocal;

  }

  bool hasPartition() const {

    return HasPartition;

  }

  StringRef getPartition() const;

  void setPartition(StringRef Part);

  // ASan, HWASan and Memtag sanitizers have some instrumentation that applies

  // specifically to global variables.

  struct SanitizerMetadata {

    SanitizerMetadata()

        : NoAddress(false), NoHWAddress(false),

          Memtag(false), IsDynInit(false) {}

    // For ASan and HWASan, this instrumentation is implicitly applied to all

    // global variables when built with -fsanitize=*. What we need is a way to

    // persist the information that a certain global variable should *not* have

    // sanitizers applied, which occurs if:

    //   1. The global variable is in the sanitizer ignore list, or

    //   2. The global variable is created by the sanitizers itself for internal

    //      usage, or

    //   3. The global variable has __attribute__((no_sanitize("..."))) or

    //      __attribute__((disable_sanitizer_instrumentation)).

    //

    // This is important, a some IR passes like GlobalMerge can delete global

    // variables and replace them with new ones. If the old variables were

    // marked to be unsanitized, then the new ones should also be.

    unsigned NoAddress : 1;

    unsigned NoHWAddress : 1;

    // Memtag sanitization works differently: sanitization is requested by clang

    // when `-fsanitize=memtag-globals` is provided, and the request can be

    // denied (and the attribute removed) by the AArch64 global tagging pass if

    // it can't be fulfilled (e.g. the global variable is a TLS variable).

    // Memtag sanitization has to interact with other parts of LLVM (like

    // supressing certain optimisations, emitting assembly directives, or

    // creating special relocation sections).

    //

    // Use `GlobalValue::isTagged()` to check whether tagging should be enabled

    // for a global variable.

    unsigned Memtag : 1;

    // ASan-specific metadata. Is this global variable dynamically initialized

    // (from a C++ language perspective), and should therefore be checked for

    // ODR violations.

    unsigned IsDynInit : 1;

  };

  bool hasSanitizerMetadata() const { return HasSanitizerMetadata; }

  const SanitizerMetadata &getSanitizerMetadata() const;

  // Note: Not byref as it's a POD and otherwise it's too easy to call

  // G.setSanitizerMetadata(G2.getSanitizerMetadata()), and the argument becomes

  // dangling when the backing storage allocates the metadata for `G`, as the

  // storage is shared between `G1` and `G2`.

  void setSanitizerMetadata(SanitizerMetadata Meta);

  void removeSanitizerMetadata();

  bool isTagged() const {

    return hasSanitizerMetadata() && getSanitizerMetadata().Memtag;

  }

  static LinkageTypes getLinkOnceLinkage(bool ODR) {

    return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;

  }

  static LinkageTypes getWeakLinkage(bool ODR) {

    return ODR ? WeakODRLinkage : WeakAnyLinkage;

  }

  static bool isExternalLinkage(LinkageTypes Linkage) {

    return Linkage == ExternalLinkage;

  }

  static bool isAvailableExternallyLinkage(LinkageTypes Linkage) {

    return Linkage == AvailableExternallyLinkage;

  }

  static bool isLinkOnceAnyLinkage(LinkageTypes Linkage) {

    return Linkage == LinkOnceAnyLinkage;

  }

  static bool isLinkOnceODRLinkage(LinkageTypes Linkage) {

    return Linkage == LinkOnceODRLinkage;

  }

  static bool isLinkOnceLinkage(LinkageTypes Linkage) {

    return isLinkOnceAnyLinkage(Linkage) || isLinkOnceODRLinkage(Linkage);

  }

  static bool isWeakAnyLinkage(LinkageTypes Linkage) {

    return Linkage == WeakAnyLinkage;

  }

  static bool isWeakODRLinkage(LinkageTypes Linkage) {

    return Linkage == WeakODRLinkage;

  }

  static bool isWeakLinkage(LinkageTypes Linkage) {

    return isWeakAnyLinkage(Linkage) || isWeakODRLinkage(Linkage);

  }

  static bool isAppendingLinkage(LinkageTypes Linkage) {

    return Linkage == AppendingLinkage;

  }

  static bool isInternalLinkage(LinkageTypes Linkage) {

    return Linkage == InternalLinkage;

  }

  static bool isPrivateLinkage(LinkageTypes Linkage) {

    return Linkage == PrivateLinkage;

  }

  static bool isLocalLinkage(LinkageTypes Linkage) {

    return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage);

  }

  static bool isExternalWeakLinkage(LinkageTypes Linkage) {

    return Linkage == ExternalWeakLinkage;

  }

  static bool isCommonLinkage(LinkageTypes Linkage) {

    return Linkage == CommonLinkage;

  }

  static bool isValidDeclarationLinkage(LinkageTypes Linkage) {

    return isExternalWeakLinkage(Linkage) || isExternalLinkage(Linkage);

  }

  /// Whether the definition of this global may be replaced by something

  /// non-equivalent at link time. For example, if a function has weak linkage

  /// then the code defining it may be replaced by different code.

  static bool isInterposableLinkage(LinkageTypes Linkage) {

    switch (Linkage) {

    case WeakAnyLinkage:

    case LinkOnceAnyLinkage:

    case CommonLinkage:

    case ExternalWeakLinkage:

      return true;

    case AvailableExternallyLinkage:

    case LinkOnceODRLinkage:

    case WeakODRLinkage:

    // The above three cannot be overridden but can be de-refined.

    case ExternalLinkage:

    case AppendingLinkage:

    case InternalLinkage:

    case PrivateLinkage:

      return false;

    }

    llvm_unreachable("Fully covered switch above!");

  }

  /// Whether the definition of this global may be discarded if it is not used

  /// in its compilation unit.

  static bool isDiscardableIfUnused(LinkageTypes Linkage) {

    return isLinkOnceLinkage(Linkage) || isLocalLinkage(Linkage) ||

           isAvailableExternallyLinkage(Linkage);

  }

  /// Whether the definition of this global may be replaced at link time.  NB:

  /// Using this method outside of the code generators is almost always a

  /// mistake: when working at the IR level use isInterposable instead as it

  /// knows about ODR semantics.

  static bool isWeakForLinker(LinkageTypes Linkage)  {

    return Linkage == WeakAnyLinkage || Linkage == WeakODRLinkage ||

           Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage ||

           Linkage == CommonLinkage || Linkage == ExternalWeakLinkage;

  }

  /// Return true if the currently visible definition of this global (if any) is

  /// exactly the definition we will see at runtime.

  ///

  /// Non-exact linkage types inhibits most non-inlining IPO, since a

  /// differently optimized variant of the same function can have different

  /// observable or undefined behavior than in the variant currently visible.

  /// For instance, we could have started with

  ///

  ///   void foo(int *v) {

  ///     int t = 5 / v[0];

  ///     (void) t;

  ///   }

  ///

  /// and "refined" it to

  ///

  ///   void foo(int *v) { }

  ///

  /// However, we cannot infer readnone for `foo`, since that would justify

  /// DSE'ing a store to `v[0]` across a call to `foo`, which can cause

  /// undefined behavior if the linker replaces the actual call destination with

  /// the unoptimized `foo`.

  ///

  /// Inlining is okay across non-exact linkage types as long as they're not

  /// interposable (see \c isInterposable), since in such cases the currently

  /// visible variant is *a* correct implementation of the original source

  /// function; it just isn't the *only* correct implementation.

  bool isDefinitionExact() const {

    return !mayBeDerefined();

  }

  /// Return true if this global has an exact defintion.

  bool hasExactDefinition() const {

    // While this computes exactly the same thing as

    // isStrongDefinitionForLinker, the intended uses are different.  This

    // function is intended to help decide if specific inter-procedural

    // transforms are correct, while isStrongDefinitionForLinker's intended use

    // is in low level code generation.

    return !isDeclaration() && isDefinitionExact();

  }

  /// Return true if this global's definition can be substituted with an

  /// *arbitrary* definition at link time or load time. We cannot do any IPO or

  /// inlining across interposable call edges, since the callee can be

  /// replaced with something arbitrary.

  bool isInterposable() const;

  bool canBenefitFromLocalAlias() const;

  bool hasExternalLinkage() const { return isExternalLinkage(getLinkage()); }

  bool hasAvailableExternallyLinkage() const {

    return isAvailableExternallyLinkage(getLinkage());

  }

  bool hasLinkOnceLinkage() const { return isLinkOnceLinkage(getLinkage()); }

  bool hasLinkOnceAnyLinkage() const {

    return isLinkOnceAnyLinkage(getLinkage());

  }

  bool hasLinkOnceODRLinkage() const {

    return isLinkOnceODRLinkage(getLinkage());

  }

  bool hasWeakLinkage() const { return isWeakLinkage(getLinkage()); }

  bool hasWeakAnyLinkage() const { return isWeakAnyLinkage(getLinkage()); }

  bool hasWeakODRLinkage() const { return isWeakODRLinkage(getLinkage()); }

  bool hasAppendingLinkage() const { return isAppendingLinkage(getLinkage()); }

  bool hasInternalLinkage() const { return isInternalLinkage(getLinkage()); }

  bool hasPrivateLinkage() const { return isPrivateLinkage(getLinkage()); }

  bool hasLocalLinkage() const { return isLocalLinkage(getLinkage()); }

  bool hasExternalWeakLinkage() const {

    return isExternalWeakLinkage(getLinkage());

  }

  bool hasCommonLinkage() const { return isCommonLinkage(getLinkage()); }

  bool hasValidDeclarationLinkage() const {

    return isValidDeclarationLinkage(getLinkage());

  }

  void setLinkage(LinkageTypes LT) {

    if (isLocalLinkage(LT)) {

      Visibility = DefaultVisibility;

      DllStorageClass = DefaultStorageClass;

    }

    Linkage = LT;

    if (isImplicitDSOLocal())

      setDSOLocal(true);

  }

  LinkageTypes getLinkage() const { return LinkageTypes(Linkage); }

  bool isDiscardableIfUnused() const {

    return isDiscardableIfUnused(getLinkage());

  }

  bool isWeakForLinker() const { return isWeakForLinker(getLinkage()); }

protected:

  /// Copy all additional attributes (those not needed to create a GlobalValue)

  /// from the GlobalValue Src to this one.

  void copyAttributesFrom(const GlobalValue *Src);

public:

  /// If the given string begins with the GlobalValue name mangling escape

  /// character '\1', drop it.

  ///

  /// This function applies a specific mangling that is used in PGO profiles,

  /// among other things. If you're trying to get a symbol name for an

  /// arbitrary GlobalValue, this is not the function you're looking for; see

  /// Mangler.h.

  static StringRef dropLLVMManglingEscape(StringRef Name) {

    if (!Name.empty() && Name[0] == '\1')

      return Name.substr(1);

    return Name;

  }

  /// Return the modified name for a global value suitable to be

  /// used as the key for a global lookup (e.g. profile or ThinLTO).

  /// The value's original name is \c Name and has linkage of type

  /// \c Linkage. The value is defined in module \c FileName.

  static std::string getGlobalIdentifier(StringRef Name,

                                         GlobalValue::LinkageTypes Linkage,

                                         StringRef FileName);

  /// Return the modified name for this global value suitable to be

  /// used as the key for a global lookup (e.g. profile or ThinLTO).

  std::string getGlobalIdentifier() const;

  /// Declare a type to represent a global unique identifier for a global value.

  /// This is a 64 bits hash that is used by PGO and ThinLTO to have a compact

  /// unique way to identify a symbol.

  using GUID = uint64_t;

  /// Return a 64-bit global unique ID constructed from global value name

  /// (i.e. returned by getGlobalIdentifier()).

  static GUID getGUID(StringRef GlobalName) { return MD5Hash(GlobalName); }

  /// Return a 64-bit global unique ID constructed from global value name

  /// (i.e. returned by getGlobalIdentifier()).

  GUID getGUID() const { return getGUID(getGlobalIdentifier()); }

  /// @name Materialization

  /// Materialization is used to construct functions only as they're needed.

  /// This

  /// is useful to reduce memory usage in LLVM or parsing work done by the

  /// BitcodeReader to load the Module.

  /// @{

  /// If this function's Module is being lazily streamed in functions from disk

  /// or some other source, this method can be used to check to see if the

  /// function has been read in yet or not.

  bool isMaterializable() const;

  /// Make sure this GlobalValue is fully read.

  Error materialize();

/// @}

  /// Return true if the primary definition of this global value is outside of

  /// the current translation unit.

  bool isDeclaration() const;

  bool isDeclarationForLinker() const {

    if (hasAvailableExternallyLinkage())

      return true;

    return isDeclaration();

  }

  /// Returns true if this global's definition will be the one chosen by the

  /// linker.

  ///

  /// NB! Ideally this should not be used at the IR level at all.  If you're

  /// interested in optimization constraints implied by the linker's ability to

  /// choose an implementation, prefer using \c hasExactDefinition.

  bool isStrongDefinitionForLinker() const {

    return !(isDeclarationForLinker() || isWeakForLinker());

  }

  const GlobalObject *getAliaseeObject() const;

  GlobalObject *getAliaseeObject() {

    return const_cast<GlobalObject *>(

        static_cast<const GlobalValue *>(this)->getAliaseeObject());

  }

  /// Returns whether this is a reference to an absolute symbol.

  bool isAbsoluteSymbolRef() const;

  /// If this is an absolute symbol reference, returns the range of the symbol,

  /// otherwise returns std::nullopt.

  std::optional<ConstantRange> getAbsoluteSymbolRange() const;

  /// This method unlinks 'this' from the containing module, but does not delete

  /// it.

  void removeFromParent();

  /// This method unlinks 'this' from the containing module and deletes it.

  void eraseFromParent();

  /// Get the module that this global value is contained inside of...

  Module *getParent() { return Parent; }

  const Module *getParent() const { return Parent; }

  // Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const Value *V) {

    return V->getValueID() == Value::FunctionVal ||

           V->getValueID() == Value::GlobalVariableVal ||

           V->getValueID() == Value::GlobalAliasVal ||

           V->getValueID() == Value::GlobalIFuncVal;

  }

  /// True if GV can be left out of the object symbol table. This is the case

  /// for linkonce_odr values whose address is not significant. While legal, it

  /// is not normally profitable to omit them from the .o symbol table. Using

  /// this analysis makes sense when the information can be passed down to the

  /// linker or we are in LTO.

  bool canBeOmittedFromSymbolTable() const;

};

} // end namespace llvm

#endif // LLVM_IR_GLOBALVALUE_H