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//===-- llvm/GlobalVariable.h - GlobalVariable class ------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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/GlobalObject.h"
#include "llvm/IR/OperandTraits.h"
namespace llvm {
class Module;
class Constant;
template<typename ValueSubClass, typename ItemParentClass>
class SymbolTableListTraits;
class GlobalVariable : public GlobalObject, public ilist_node<GlobalVariable> {
friend class SymbolTableListTraits<GlobalVariable, Module>;
void *operator new(size_t, unsigned) = delete;
void operator=(const GlobalVariable &) = delete;
GlobalVariable(const GlobalVariable &) = delete;
void setParent(Module *parent);
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:
// allocate space for exactly one operand
void *operator new(size_t s) {
return User::operator new(s, 1);
}
/// 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, unsigned AddressSpace = 0,
bool isExternallyInitialized = false);
~GlobalVariable() {
NumOperands = 1; // FIXME: needed by operator delete
}
/// 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 with weak linkage may change at
// link time.
!mayBeOverridden() &&
// 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 hasInitializer() &&
// It's not safe to modify initializers of global variables with weak
// linkage, because the linker might choose to discard the initializer and
// use the initializer from another instance of the global variable
// instead. It is wrong to modify the initializer of a global variable
// with *_odr linkage because then different instances of the global may
// have different initializers, breaking the One Definition Rule.
!isWeakForLinker() &&
// 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 GlobalValue *Src) override;
/// removeFromParent - This method unlinks 'this' from the containing module,
/// but does not delete it.
///
void removeFromParent() override;
/// eraseFromParent - This method unlinks 'this' from the containing module
/// and deletes it.
///
void eraseFromParent() override;
/// Override Constant's implementation of this method so we can
/// replace constant initializers.
void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U) override;
// Methods for support type inquiry through isa, cast, and dyn_cast:
static inline bool classof(const Value *V) {
return V->getValueID() == Value::GlobalVariableVal;
}
};
template <>
struct OperandTraits<GlobalVariable> :
public OptionalOperandTraits<GlobalVariable> {
};
DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GlobalVariable, Value)
} // End llvm namespace
#endif
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