1 //===-- llvm/GlobalValue.h - Class to represent a global value --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file is a common base class of all globally definable objects. As such,
11 // it is subclassed by GlobalVariable and by Function. This is used because you
12 // can do certain things with these global objects that you can't do to anything
13 // else. For example, use the address of one as a constant.
15 //===----------------------------------------------------------------------===//
17 #ifndef LLVM_GLOBALVALUE_H
18 #define LLVM_GLOBALVALUE_H
20 #include "llvm/Constant.h"
27 class GlobalValue : public Constant {
28 GlobalValue(const GlobalValue &); // do not implement
31 ExternalLinkage, // Externally visible function
32 LinkOnceLinkage, // Keep one copy of named function when linking (inline)
33 WeakLinkage, // Keep one copy of named function when linking (weak)
34 AppendingLinkage, // Special purpose, only applies to global arrays
35 InternalLinkage // Rename collisions when linking (static functions)
38 GlobalValue(const Type *Ty, ValueTy vty, LinkageTypes linkage,
39 const std::string &name = "")
40 : Constant(Ty, vty, name), Linkage(linkage), Parent(0) { }
42 LinkageTypes Linkage; // The linkage of this global
46 removeDeadConstantUsers(); // remove any dead constants using this.
49 /// If the usage is empty (except transitively dead constants), then this
50 /// global value can can be safely deleted since the destructor will
51 /// delete the dead constants as well.
52 /// @brief Determine if the usage of this global value is empty except
53 /// for transitively dead constants.
54 bool use_empty_except_constants();
56 /// getType - Global values are always pointers.
57 inline const PointerType *getType() const {
58 return reinterpret_cast<const PointerType*>(User::getType());
61 bool hasExternalLinkage() const { return Linkage == ExternalLinkage; }
62 bool hasLinkOnceLinkage() const { return Linkage == LinkOnceLinkage; }
63 bool hasWeakLinkage() const { return Linkage == WeakLinkage; }
64 bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; }
65 bool hasInternalLinkage() const { return Linkage == InternalLinkage; }
66 void setLinkage(LinkageTypes LT) { Linkage = LT; }
67 LinkageTypes getLinkage() const { return Linkage; }
69 /// Override from Constant class. No GlobalValue's have null values so
70 /// this always returns false.
71 virtual bool isNullValue() const { return false; }
73 /// Override from Constant class.
74 virtual void destroyConstant();
76 /// isExternal - Return true if the primary definition of this global value is
77 /// outside of the current translation unit...
78 virtual bool isExternal() const = 0;
80 /// getParent - Get the module that this global value is contained inside
82 inline Module *getParent() { return Parent; }
83 inline const Module *getParent() const { return Parent; }
85 /// removeDeadConstantUsers - If there are any dead constant users dangling
86 /// off of this global value, remove them. This method is useful for clients
87 /// that want to check to see if a global is unused, but don't want to deal
88 /// with potentially dead constants hanging off of the globals.
90 /// This method tries to make the global dead. If it detects a user that
91 /// would prevent it from becoming completely dead, it gives up early,
92 /// potentially leaving some dead constant users around.
93 void removeDeadConstantUsers();
95 // Methods for support type inquiry through isa, cast, and dyn_cast:
96 static inline bool classof(const GlobalValue *T) { return true; }
97 static inline bool classof(const Value *V) {
98 return V->getValueType() == Value::FunctionVal ||
99 V->getValueType() == Value::GlobalVariableVal;
103 } // End llvm namespace