1 //===-- llvm/GlobalValue.h - Class to represent a global value --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // 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, GlobalAlias and by Function. This is
12 // used because you can do certain things with these global objects that you
13 // can't do to anything else. For example, use the address of one as a
16 //===----------------------------------------------------------------------===//
18 #ifndef LLVM_GLOBALVALUE_H
19 #define LLVM_GLOBALVALUE_H
21 #include "llvm/Constant.h"
28 class GlobalValue : public Constant {
29 GlobalValue(const GlobalValue &); // do not implement
31 /// @brief An enumeration for the kinds of linkage for global values.
33 ExternalLinkage = 0,///< Externally visible function
34 LinkOnceAnyLinkage, ///< Keep one copy of function when linking (inline)
35 LinkOnceODRLinkage, ///< Same, but only replaced by something equivalent.
36 WeakAnyLinkage, ///< Keep one copy of named function when linking (weak)
37 WeakODRLinkage, ///< Same, but only replaced by something equivalent.
38 AppendingLinkage, ///< Special purpose, only applies to global arrays
39 InternalLinkage, ///< Rename collisions when linking (static functions)
40 PrivateLinkage, ///< Like Internal, but omit from symbol table
41 DLLImportLinkage, ///< Function to be imported from DLL
42 DLLExportLinkage, ///< Function to be accessible from DLL
43 ExternalWeakLinkage,///< ExternalWeak linkage description
44 GhostLinkage, ///< Stand-in functions for streaming fns from BC files
45 CommonLinkage ///< Tentative definitions
48 /// @brief An enumeration for the kinds of visibility of global values.
49 enum VisibilityTypes {
50 DefaultVisibility = 0, ///< The GV is visible
51 HiddenVisibility, ///< The GV is hidden
52 ProtectedVisibility ///< The GV is protected
56 GlobalValue(const Type *ty, ValueTy vty, Use *Ops, unsigned NumOps,
57 LinkageTypes linkage, const std::string &name = "")
58 : Constant(ty, vty, Ops, NumOps), Parent(0),
59 Linkage(linkage), Visibility(DefaultVisibility), Alignment(0) {
60 if (!name.empty()) setName(name);
64 // Note: VC++ treats enums as signed, so an extra bit is required to prevent
65 // Linkage and Visibility from turning into negative values.
66 LinkageTypes Linkage : 5; // The linkage of this global
67 unsigned Visibility : 2; // The visibility style of this global
68 unsigned Alignment : 16; // Alignment of this symbol, must be power of two
69 std::string Section; // Section to emit this into, empty mean default
72 removeDeadConstantUsers(); // remove any dead constants using this.
75 unsigned getAlignment() const { return Alignment; }
76 void setAlignment(unsigned Align) {
77 assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
81 VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
82 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
83 bool hasProtectedVisibility() const {
84 return Visibility == ProtectedVisibility;
86 void setVisibility(VisibilityTypes V) { Visibility = V; }
88 bool hasSection() const { return !Section.empty(); }
89 const std::string &getSection() const { return Section; }
90 void setSection(const std::string &S) { Section = S; }
92 /// If the usage is empty (except transitively dead constants), then this
93 /// global value can can be safely deleted since the destructor will
94 /// delete the dead constants as well.
95 /// @brief Determine if the usage of this global value is empty except
96 /// for transitively dead constants.
97 bool use_empty_except_constants();
99 /// getType - Global values are always pointers.
100 inline const PointerType *getType() const {
101 return reinterpret_cast<const PointerType*>(User::getType());
104 static LinkageTypes getLinkOnceLinkage(bool ODR) {
105 return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;
107 static LinkageTypes getWeakLinkage(bool ODR) {
108 return ODR ? WeakODRLinkage : WeakAnyLinkage;
111 bool hasExternalLinkage() const { return Linkage == ExternalLinkage; }
112 bool hasLinkOnceLinkage() const {
113 return Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage;
115 bool hasWeakLinkage() const {
116 return Linkage == WeakAnyLinkage || Linkage == WeakODRLinkage;
118 bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; }
119 bool hasInternalLinkage() const { return Linkage == InternalLinkage; }
120 bool hasPrivateLinkage() const { return Linkage == PrivateLinkage; }
121 bool hasLocalLinkage() const {
122 return Linkage == InternalLinkage || Linkage == PrivateLinkage;
124 bool hasDLLImportLinkage() const { return Linkage == DLLImportLinkage; }
125 bool hasDLLExportLinkage() const { return Linkage == DLLExportLinkage; }
126 bool hasExternalWeakLinkage() const { return Linkage == ExternalWeakLinkage; }
127 bool hasGhostLinkage() const { return Linkage == GhostLinkage; }
128 bool hasCommonLinkage() const { return Linkage == CommonLinkage; }
130 void setLinkage(LinkageTypes LT) { Linkage = LT; }
131 LinkageTypes getLinkage() const { return Linkage; }
133 /// mayBeOverridden - Whether the definition of this global may be replaced
134 /// by something non-equivalent at link time. For example, if a function has
135 /// weak linkage then the code defining it may be replaced by different code.
136 bool mayBeOverridden() const {
137 return (Linkage == WeakAnyLinkage ||
138 Linkage == LinkOnceAnyLinkage ||
139 Linkage == CommonLinkage ||
140 Linkage == ExternalWeakLinkage);
143 /// isWeakForLinker - Whether the definition of this global may be replaced at
144 /// link time, whether the replacement is equivalent to the original or not.
145 bool isWeakForLinker() const {
146 return (Linkage == WeakAnyLinkage ||
147 Linkage == WeakODRLinkage ||
148 Linkage == LinkOnceAnyLinkage ||
149 Linkage == LinkOnceODRLinkage ||
150 Linkage == CommonLinkage ||
151 Linkage == ExternalWeakLinkage);
154 /// copyAttributesFrom - copy all additional attributes (those not needed to
155 /// create a GlobalValue) from the GlobalValue Src to this one.
156 virtual void copyAttributesFrom(const GlobalValue *Src);
158 /// hasNotBeenReadFromBitcode - If a module provider is being used to lazily
159 /// stream in functions from disk, this method can be used to check to see if
160 /// the function has been read in yet or not. Unless you are working on the
161 /// JIT or something else that streams stuff in lazily, you don't need to
162 /// worry about this.
163 bool hasNotBeenReadFromBitcode() const { return Linkage == GhostLinkage; }
165 /// Override from Constant class. No GlobalValue's are null values so this
166 /// always returns false.
167 virtual bool isNullValue() const { return false; }
169 /// Override from Constant class.
170 virtual void destroyConstant();
172 /// isDeclaration - Return true if the primary definition of this global
173 /// value is outside of the current translation unit...
174 virtual bool isDeclaration() const = 0;
176 /// removeFromParent - This method unlinks 'this' from the containing module,
177 /// but does not delete it.
178 virtual void removeFromParent() = 0;
180 /// eraseFromParent - This method unlinks 'this' from the containing module
182 virtual void eraseFromParent() = 0;
184 /// getParent - Get the module that this global value is contained inside
186 inline Module *getParent() { return Parent; }
187 inline const Module *getParent() const { return Parent; }
189 /// removeDeadConstantUsers - If there are any dead constant users dangling
190 /// off of this global value, remove them. This method is useful for clients
191 /// that want to check to see if a global is unused, but don't want to deal
192 /// with potentially dead constants hanging off of the globals.
193 void removeDeadConstantUsers() const;
195 // Methods for support type inquiry through isa, cast, and dyn_cast:
196 static inline bool classof(const GlobalValue *) { return true; }
197 static inline bool classof(const Value *V) {
198 return V->getValueID() == Value::FunctionVal ||
199 V->getValueID() == Value::GlobalVariableVal ||
200 V->getValueID() == Value::GlobalAliasVal;
204 } // End llvm namespace