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//===-- llvm/GlobalVariable.h - GlobalVariable class ------------*- 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 contains the declaration of the GlobalVariable class, which

// represents a single global variable (or constant) in the VM.

//

// Global variables are constant pointers that refer to hunks of space that are

// allocated by either the VM, or by the linker in a static compiler.  A global

// variable may have an initial value, which is copied into the executables .data

// area.  Global Constants are required to have initializers.

//

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

#ifndef LLVM_IR_GLOBALVARIABLE_H

#define LLVM_IR_GLOBALVARIABLE_H

#include "llvm/ADT/Twine.h"

#include "llvm/ADT/ilist_node.h"

#include "llvm/IR/Attributes.h"

#include "llvm/IR/GlobalObject.h"

#include "llvm/IR/OperandTraits.h"

#include "llvm/IR/Value.h"

#include <cassert>

#include <cstddef>

namespace llvm {

class Constant;

class Module;

template <typename ValueSubClass> class SymbolTableListTraits;

class DIGlobalVariableExpression;

class GlobalVariable : public GlobalObject, public ilist_node<GlobalVariable> {

  friend class SymbolTableListTraits<GlobalVariable>;

  AttributeSet Attrs;

  bool isConstantGlobal : 1;                   // Is this a global constant?

  bool isExternallyInitializedConstant : 1;    // Is this a global whose value

                                               // can change from its initial

                                               // value before global

                                               // initializers are run?

public:

  /// GlobalVariable ctor - If a parent module is specified, the global is

  /// automatically inserted into the end of the specified modules global list.

  GlobalVariable(Type *Ty, bool isConstant, LinkageTypes Linkage,

                 Constant *Initializer = nullptr, const Twine &Name = "",

                 ThreadLocalMode = NotThreadLocal, unsigned AddressSpace = 0,

                 bool isExternallyInitialized = false);

  /// GlobalVariable ctor - This creates a global and inserts it before the

  /// specified other global.

  GlobalVariable(Module &M, Type *Ty, bool isConstant, LinkageTypes Linkage,

                 Constant *Initializer, const Twine &Name = "",

                 GlobalVariable *InsertBefore = nullptr,

                 ThreadLocalMode = NotThreadLocal,

                 std::optional<unsigned> AddressSpace = std::nullopt,

                 bool isExternallyInitialized = false);

  GlobalVariable(const GlobalVariable &) = delete;

  GlobalVariable &operator=(const GlobalVariable &) = delete;

  ~GlobalVariable() {

    dropAllReferences();

  }

  // allocate space for exactly one operand

  void *operator new(size_t s) {

    return User::operator new(s, 1);

  }

  // delete space for exactly one operand as created in the corresponding new operator

  void operator delete(void *ptr){

    assert(ptr != nullptr && "must not be nullptr");

    User *Obj = static_cast<User *>(ptr);

    // Number of operands can be set to 0 after construction and initialization. Make sure

    // that number of operands is reset to 1, as this is needed in User::operator delete

    Obj->setGlobalVariableNumOperands(1);

    User::operator delete(Obj);

  }

  /// Provide fast operand accessors

  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);

  /// Definitions have initializers, declarations don't.

  ///

  inline bool hasInitializer() const { return !isDeclaration(); }

  /// hasDefinitiveInitializer - Whether the global variable has an initializer,

  /// and any other instances of the global (this can happen due to weak

  /// linkage) are guaranteed to have the same initializer.

  ///

  /// Note that if you want to transform a global, you must use

  /// hasUniqueInitializer() instead, because of the *_odr linkage type.

  ///

  /// Example:

  ///

  /// @a = global SomeType* null - Initializer is both definitive and unique.

  ///

  /// @b = global weak SomeType* null - Initializer is neither definitive nor

  /// unique.

  ///

  /// @c = global weak_odr SomeType* null - Initializer is definitive, but not

  /// unique.

  inline bool hasDefinitiveInitializer() const {

    return hasInitializer() &&

      // The initializer of a global variable may change to something arbitrary

      // at link time.

      !isInterposable() &&

      // The initializer of a global variable with the externally_initialized

      // marker may change at runtime before C++ initializers are evaluated.

      !isExternallyInitialized();

  }

  /// hasUniqueInitializer - Whether the global variable has an initializer, and

  /// any changes made to the initializer will turn up in the final executable.

  inline bool hasUniqueInitializer() const {

    return

        // We need to be sure this is the definition that will actually be used

        isStrongDefinitionForLinker() &&

        // It is not safe to modify initializers of global variables with the

        // external_initializer marker since the value may be changed at runtime

        // before C++ initializers are evaluated.

        !isExternallyInitialized();

  }

  /// getInitializer - Return the initializer for this global variable.  It is

  /// illegal to call this method if the global is external, because we cannot

  /// tell what the value is initialized to!

  ///

  inline const Constant *getInitializer() const {

    assert(hasInitializer() && "GV doesn't have initializer!");

    return static_cast<Constant*>(Op<0>().get());

  }

  inline Constant *getInitializer() {

    assert(hasInitializer() && "GV doesn't have initializer!");

    return static_cast<Constant*>(Op<0>().get());

  }

  /// setInitializer - Sets the initializer for this global variable, removing

  /// any existing initializer if InitVal==NULL.  If this GV has type T*, the

  /// initializer must have type T.

  void setInitializer(Constant *InitVal);

  /// If the value is a global constant, its value is immutable throughout the

  /// runtime execution of the program.  Assigning a value into the constant

  /// leads to undefined behavior.

  ///

  bool isConstant() const { return isConstantGlobal; }

  void setConstant(bool Val) { isConstantGlobal = Val; }

  bool isExternallyInitialized() const {

    return isExternallyInitializedConstant;

  }

  void setExternallyInitialized(bool Val) {

    isExternallyInitializedConstant = Val;

  }

  /// copyAttributesFrom - copy all additional attributes (those not needed to

  /// create a GlobalVariable) from the GlobalVariable Src to this one.

  void copyAttributesFrom(const GlobalVariable *Src);

  /// removeFromParent - This method unlinks 'this' from the containing module,

  /// but does not delete it.

  ///

  void removeFromParent();

  /// eraseFromParent - This method unlinks 'this' from the containing module

  /// and deletes it.

  ///

  void eraseFromParent();

  /// Drop all references in preparation to destroy the GlobalVariable. This

  /// drops not only the reference to the initializer but also to any metadata.

  void dropAllReferences();

  /// Attach a DIGlobalVariableExpression.

  void addDebugInfo(DIGlobalVariableExpression *GV);

  /// Fill the vector with all debug info attachements.

  void getDebugInfo(SmallVectorImpl<DIGlobalVariableExpression *> &GVs) const;

  /// Add attribute to this global.

  void addAttribute(Attribute::AttrKind Kind) {

    Attrs = Attrs.addAttribute(getContext(), Kind);

  }

  /// Add attribute to this global.

  void addAttribute(StringRef Kind, StringRef Val = StringRef()) {

    Attrs = Attrs.addAttribute(getContext(), Kind, Val);

  }

  /// Return true if the attribute exists.

  bool hasAttribute(Attribute::AttrKind Kind) const {

    return Attrs.hasAttribute(Kind);

  }

  /// Return true if the attribute exists.

  bool hasAttribute(StringRef Kind) const {

    return Attrs.hasAttribute(Kind);

  }

  /// Return true if any attributes exist.

  bool hasAttributes() const {

    return Attrs.hasAttributes();

  }

  /// Return the attribute object.

  Attribute getAttribute(Attribute::AttrKind Kind) const {

    return Attrs.getAttribute(Kind);

  }

  /// Return the attribute object.

  Attribute getAttribute(StringRef Kind) const {

    return Attrs.getAttribute(Kind);

  }

  /// Return the attribute set for this global

  AttributeSet getAttributes() const {

    return Attrs;

  }

  /// Return attribute set as list with index.

  /// FIXME: This may not be required once ValueEnumerators

  /// in bitcode-writer can enumerate attribute-set.

  AttributeList getAttributesAsList(unsigned index) const {

    if (!hasAttributes())

      return AttributeList();

    std::pair<unsigned, AttributeSet> AS[1] = {{index, Attrs}};

    return AttributeList::get(getContext(), AS);

  }

  /// Set attribute list for this global

  void setAttributes(AttributeSet A) {

    Attrs = A;

  }

  /// Check if section name is present

  bool hasImplicitSection() const {

    return getAttributes().hasAttribute("bss-section") ||

           getAttributes().hasAttribute("data-section") ||

           getAttributes().hasAttribute("relro-section") ||

           getAttributes().hasAttribute("rodata-section");

  }

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

  static bool classof(const Value *V) {

    return V->getValueID() == Value::GlobalVariableVal;

  }

};

template <>

struct OperandTraits<GlobalVariable> :

  public OptionalOperandTraits<GlobalVariable> {

};

DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GlobalVariable, Value)

} // end namespace llvm

#endif // LLVM_IR_GLOBALVARIABLE_H