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)
36 GhostLinkage // Stand-in functions for streaming fns from BC files
39 GlobalValue(const Type *Ty, ValueTy vty, LinkageTypes linkage,
40 const std::string &name = "")
41 : Constant(Ty, vty, name), Linkage(linkage), Parent(0) { }
43 LinkageTypes Linkage; // The linkage of this global
47 removeDeadConstantUsers(); // remove any dead constants using this.
50 /// If the usage is empty (except transitively dead constants), then this
51 /// global value can can be safely deleted since the destructor will
52 /// delete the dead constants as well.
53 /// @brief Determine if the usage of this global value is empty except
54 /// for transitively dead constants.
55 bool use_empty_except_constants();
57 /// getType - Global values are always pointers.
58 inline const PointerType *getType() const {
59 return reinterpret_cast<const PointerType*>(User::getType());
62 bool hasExternalLinkage() const { return Linkage == ExternalLinkage; }
63 bool hasLinkOnceLinkage() const { return Linkage == LinkOnceLinkage; }
64 bool hasWeakLinkage() const { return Linkage == WeakLinkage; }
65 bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; }
66 bool hasInternalLinkage() const { return Linkage == InternalLinkage; }
67 void setLinkage(LinkageTypes LT) { Linkage = LT; }
68 LinkageTypes getLinkage() const { return Linkage; }
70 /// hasNotBeenReadFromBytecode - If a module provider is being used to lazily
71 /// stream in functions from disk, this method can be used to check to see if
72 /// the function has been read in yet or not. Unless you are working on the
73 /// JIT or something else that streams stuff in lazily, you don't need to
75 bool hasNotBeenReadFromBytecode() const { return Linkage == GhostLinkage; }
77 /// Override from Constant class. No GlobalValue's are null values so this
78 /// always returns false.
79 virtual bool isNullValue() const { return false; }
81 /// Override from Constant class.
82 virtual void destroyConstant();
84 /// isExternal - Return true if the primary definition of this global value is
85 /// outside of the current translation unit...
86 virtual bool isExternal() const = 0;
88 /// getParent - Get the module that this global value is contained inside
90 inline Module *getParent() { return Parent; }
91 inline const Module *getParent() const { return Parent; }
93 /// removeDeadConstantUsers - If there are any dead constant users dangling
94 /// off of this global value, remove them. This method is useful for clients
95 /// that want to check to see if a global is unused, but don't want to deal
96 /// with potentially dead constants hanging off of the globals.
98 /// This method tries to make the global dead. If it detects a user that
99 /// would prevent it from becoming completely dead, it gives up early,
100 /// potentially leaving some dead constant users around.
101 void removeDeadConstantUsers();
103 // Methods for support type inquiry through isa, cast, and dyn_cast:
104 static inline bool classof(const GlobalValue *T) { return true; }
105 static inline bool classof(const Value *V) {
106 return V->getValueType() == Value::FunctionVal ||
107 V->getValueType() == Value::GlobalVariableVal;
111 } // End llvm namespace