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//===-- llvm/GlobalValue.h - Class to represent a global value --*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
// This file is a common base class of all globally definable objects. As such,
// it is subclassed by GlobalVariable 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.
#include "llvm/Constant.h"
namespace llvm {
class PointerType;
class Module;
class GlobalValue : public Constant {
GlobalValue(const GlobalValue &); // do not implement
enum LinkageTypes {
ExternalLinkage, /// Externally visible function
LinkOnceLinkage, /// Keep one copy of named function when linking (inline)
WeakLinkage, /// Keep one copy of named function when linking (weak)
AppendingLinkage, /// Special purpose, only applies to global arrays
InternalLinkage, /// Rename collisions when linking (static functions)
GhostLinkage /// Stand-in functions for streaming fns from BC files
GlobalValue(const Type *Ty, ValueTy vty, Use *Ops, unsigned NumOps,
LinkageTypes linkage, const std::string &name = "")
: Constant(Ty, vty, Ops, NumOps, name), Linkage(linkage), Parent(0) { }
LinkageTypes Linkage; // The linkage of this global
Module *Parent;
~GlobalValue() {
removeDeadConstantUsers(); // remove any dead constants using this.
/// If the usage is empty (except transitively dead constants), then this
/// global value can can be safely deleted since the destructor will
/// delete the dead constants as well.
/// @brief Determine if the usage of this global value is empty except
/// for transitively dead constants.
bool use_empty_except_constants();
/// getType - Global values are always pointers.
inline const PointerType *getType() const {
return reinterpret_cast<const PointerType*>(User::getType());
bool hasExternalLinkage() const { return Linkage == ExternalLinkage; }
bool hasLinkOnceLinkage() const { return Linkage == LinkOnceLinkage; }
bool hasWeakLinkage() const { return Linkage == WeakLinkage; }
bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; }
bool hasInternalLinkage() const { return Linkage == InternalLinkage; }
void setLinkage(LinkageTypes LT) { Linkage = LT; }
LinkageTypes getLinkage() const { return Linkage; }
/// hasNotBeenReadFromBytecode - If a module provider is being used to lazily
/// stream in functions from disk, this method can be used to check to see if
/// the function has been read in yet or not. Unless you are working on the
/// JIT or something else that streams stuff in lazily, you don't need to
/// worry about this.
bool hasNotBeenReadFromBytecode() const { return Linkage == GhostLinkage; }
/// Override from Constant class. No GlobalValue's are null values so this
/// always returns false.
virtual bool isNullValue() const { return false; }
/// Override from Constant class.
virtual void destroyConstant();
/// isExternal - Return true if the primary definition of this global value is
/// outside of the current translation unit...
virtual bool isExternal() const = 0;
/// getParent - Get the module that this global value is contained inside
/// of...
inline Module *getParent() { return Parent; }
inline const Module *getParent() const { return Parent; }
/// removeDeadConstantUsers - If there are any dead constant users dangling
/// off of this global value, remove them. This method is useful for clients
/// that want to check to see if a global is unused, but don't want to deal
/// with potentially dead constants hanging off of the globals.
/// This method tries to make the global dead. If it detects a user that
/// would prevent it from becoming completely dead, it gives up early,
/// potentially leaving some dead constant users around.
void removeDeadConstantUsers();
// Methods for support type inquiry through isa, cast, and dyn_cast:
static inline bool classof(const GlobalValue *) { return true; }
static inline bool classof(const Value *V) {
return V->getValueType() == Value::FunctionVal ||
V->getValueType() == Value::GlobalVariableVal;
} // End llvm namespace