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//===-- llvm/GlobalValue.h - Class to represent a global value --*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file 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, 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_GLOBALVALUE_H
#define LLVM_GLOBALVALUE_H
#include "llvm/Constant.h"
namespace llvm {
class PointerType;
class Module;
class GlobalValue : public Constant {
GlobalValue(const GlobalValue &); // do not implement
public:
/// @brief An enumeration for the kinds of linkage for global values.
enum LinkageTypes {
ExternalLinkage = 0,///< Externally visible function
LinkOnceLinkage, ///< Keep one copy of 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)
PrivateLinkage, ///< Like Internal, but omit from symbol table
DLLImportLinkage, ///< Function to be imported from DLL
DLLExportLinkage, ///< Function to be accessible from DLL
ExternalWeakLinkage,///< ExternalWeak linkage description
GhostLinkage, ///< Stand-in functions for streaming fns from BC files
CommonLinkage ///< Tentative definitions
};
/// @brief 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
};
protected:
GlobalValue(const Type *ty, ValueTy vty, Use *Ops, unsigned NumOps,
LinkageTypes linkage, const std::string &name = "")
: Constant(ty, vty, Ops, NumOps), Parent(0),
Linkage(linkage), Visibility(DefaultVisibility), Alignment(0) {
if (!name.empty()) setName(name);
}
Module *Parent;
// Note: VC++ treats enums as signed, so an extra bit is required to prevent
// Linkage and Visibility from turning into negative values.
LinkageTypes Linkage : 5; // The linkage of this global
unsigned Visibility : 2; // The visibility style of this global
unsigned Alignment : 16; // Alignment of this symbol, must be power of two
std::string Section; // Section to emit this into, empty mean default
public:
~GlobalValue() {
removeDeadConstantUsers(); // remove any dead constants using this.
}
unsigned getAlignment() const { return Alignment; }
void setAlignment(unsigned Align) {
assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
Alignment = Align;
}
VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
bool hasProtectedVisibility() const {
return Visibility == ProtectedVisibility;
}
void setVisibility(VisibilityTypes V) { Visibility = V; }
bool hasSection() const { return !Section.empty(); }
const std::string &getSection() const { return Section; }
void setSection(const std::string &S) { Section = S; }
/// 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 hasCommonLinkage() const { return Linkage == CommonLinkage; }
bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; }
bool hasInternalLinkage() const { return Linkage == InternalLinkage; }
bool hasPrivateLinkage() const { return Linkage == PrivateLinkage; }
bool hasLocalLinkage() const {
return Linkage == InternalLinkage || Linkage == PrivateLinkage;
}
bool hasDLLImportLinkage() const { return Linkage == DLLImportLinkage; }
bool hasDLLExportLinkage() const { return Linkage == DLLExportLinkage; }
bool hasExternalWeakLinkage() const { return Linkage == ExternalWeakLinkage; }
bool hasGhostLinkage() const { return Linkage == GhostLinkage; }
void setLinkage(LinkageTypes LT) { Linkage = LT; }
LinkageTypes getLinkage() const { return Linkage; }
/// mayBeOverridden - Whether the definition of this global may be replaced
/// at link time. For example, if a function has weak linkage then the code
/// defining it may be replaced by different code.
bool mayBeOverridden() const {
return (Linkage == WeakLinkage ||
Linkage == LinkOnceLinkage ||
Linkage == CommonLinkage ||
Linkage == ExternalWeakLinkage);
}
/// copyAttributesFrom - copy all additional attributes (those not needed to
/// create a GlobalValue) from the GlobalValue Src to this one.
virtual void copyAttributesFrom(const GlobalValue *Src);
/// hasNotBeenReadFromBitcode - 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 hasNotBeenReadFromBitcode() 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();
/// isDeclaration - Return true if the primary definition of this global
/// value is outside of the current translation unit...
virtual bool isDeclaration() const = 0;
/// removeFromParent - This method unlinks 'this' from the containing module,
/// but does not delete it.
virtual void removeFromParent() = 0;
/// eraseFromParent - This method unlinks 'this' from the containing module
/// and deletes it.
virtual void eraseFromParent() = 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.
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->getValueID() == Value::FunctionVal ||
V->getValueID() == Value::GlobalVariableVal ||
V->getValueID() == Value::GlobalAliasVal;
}
};
} // End llvm namespace
#endif
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