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 AvailableExternallyLinkage, ///< Available for inspection, not emission.
35 LinkOnceAnyLinkage, ///< Keep one copy of function when linking (inline)
36 LinkOnceODRLinkage, ///< Same, but only replaced by something equivalent.
37 WeakAnyLinkage, ///< Keep one copy of named function when linking (weak)
38 WeakODRLinkage, ///< Same, but only replaced by something equivalent.
39 AppendingLinkage, ///< Special purpose, only applies to global arrays
40 InternalLinkage, ///< Rename collisions when linking (static functions)
41 PrivateLinkage, ///< Like Internal, but omit from symbol table
42 DLLImportLinkage, ///< Function to be imported from DLL
43 DLLExportLinkage, ///< Function to be accessible from DLL
44 ExternalWeakLinkage,///< ExternalWeak linkage description
45 GhostLinkage, ///< Stand-in functions for streaming fns from BC files
46 CommonLinkage ///< Tentative definitions
49 /// @brief An enumeration for the kinds of visibility of global values.
50 enum VisibilityTypes {
51 DefaultVisibility = 0, ///< The GV is visible
52 HiddenVisibility, ///< The GV is hidden
53 ProtectedVisibility ///< The GV is protected
57 GlobalValue(const Type *ty, ValueTy vty, Use *Ops, unsigned NumOps,
58 LinkageTypes linkage, const std::string &name = "")
59 : Constant(ty, vty, Ops, NumOps), Parent(0),
60 Linkage(linkage), Visibility(DefaultVisibility), Alignment(0) {
61 if (!name.empty()) setName(name);
65 // Note: VC++ treats enums as signed, so an extra bit is required to prevent
66 // Linkage and Visibility from turning into negative values.
67 LinkageTypes Linkage : 5; // The linkage of this global
68 unsigned Visibility : 2; // The visibility style of this global
69 unsigned Alignment : 16; // Alignment of this symbol, must be power of two
70 std::string Section; // Section to emit this into, empty mean default
73 removeDeadConstantUsers(); // remove any dead constants using this.
76 unsigned getAlignment() const { return Alignment; }
77 void setAlignment(unsigned Align) {
78 assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
82 VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
83 bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; }
84 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
85 bool hasProtectedVisibility() const {
86 return Visibility == ProtectedVisibility;
88 void setVisibility(VisibilityTypes V) { Visibility = V; }
90 bool hasSection() const { return !Section.empty(); }
91 const std::string &getSection() const { return Section; }
92 void setSection(const std::string &S) { Section = S; }
94 /// If the usage is empty (except transitively dead constants), then this
95 /// global value can can be safely deleted since the destructor will
96 /// delete the dead constants as well.
97 /// @brief Determine if the usage of this global value is empty except
98 /// for transitively dead constants.
99 bool use_empty_except_constants();
101 /// getType - Global values are always pointers.
102 inline const PointerType *getType() const {
103 return reinterpret_cast<const PointerType*>(User::getType());
106 static LinkageTypes getLinkOnceLinkage(bool ODR) {
107 return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;
109 static LinkageTypes getWeakLinkage(bool ODR) {
110 return ODR ? WeakODRLinkage : WeakAnyLinkage;
113 bool hasExternalLinkage() const { return Linkage == ExternalLinkage; }
114 bool hasAvailableExternallyLinkage() const {
115 return Linkage == AvailableExternallyLinkage;
117 bool hasLinkOnceLinkage() const {
118 return Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage;
120 bool hasWeakLinkage() const {
121 return Linkage == WeakAnyLinkage || Linkage == WeakODRLinkage;
123 bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; }
124 bool hasInternalLinkage() const { return Linkage == InternalLinkage; }
125 bool hasPrivateLinkage() const { return Linkage == PrivateLinkage; }
126 bool hasLocalLinkage() const {
127 return Linkage == InternalLinkage || Linkage == PrivateLinkage;
129 bool hasDLLImportLinkage() const { return Linkage == DLLImportLinkage; }
130 bool hasDLLExportLinkage() const { return Linkage == DLLExportLinkage; }
131 bool hasExternalWeakLinkage() const { return Linkage == ExternalWeakLinkage; }
132 bool hasGhostLinkage() const { return Linkage == GhostLinkage; }
133 bool hasCommonLinkage() const { return Linkage == CommonLinkage; }
135 void setLinkage(LinkageTypes LT) { Linkage = LT; }
136 LinkageTypes getLinkage() const { return Linkage; }
138 /// mayBeOverridden - Whether the definition of this global may be replaced
139 /// by something non-equivalent at link time. For example, if a function has
140 /// weak linkage then the code defining it may be replaced by different code.
141 bool mayBeOverridden() const {
142 return (Linkage == WeakAnyLinkage ||
143 Linkage == LinkOnceAnyLinkage ||
144 Linkage == CommonLinkage ||
145 Linkage == ExternalWeakLinkage);
148 /// isWeakForLinker - Whether the definition of this global may be replaced at
150 bool isWeakForLinker() const {
151 return (Linkage == AvailableExternallyLinkage ||
152 Linkage == WeakAnyLinkage ||
153 Linkage == WeakODRLinkage ||
154 Linkage == LinkOnceAnyLinkage ||
155 Linkage == LinkOnceODRLinkage ||
156 Linkage == CommonLinkage ||
157 Linkage == ExternalWeakLinkage);
160 /// copyAttributesFrom - copy all additional attributes (those not needed to
161 /// create a GlobalValue) from the GlobalValue Src to this one.
162 virtual void copyAttributesFrom(const GlobalValue *Src);
164 /// hasNotBeenReadFromBitcode - If a module provider is being used to lazily
165 /// stream in functions from disk, this method can be used to check to see if
166 /// the function has been read in yet or not. Unless you are working on the
167 /// JIT or something else that streams stuff in lazily, you don't need to
168 /// worry about this.
169 bool hasNotBeenReadFromBitcode() const { return Linkage == GhostLinkage; }
171 /// Override from Constant class. No GlobalValue's are null values so this
172 /// always returns false.
173 virtual bool isNullValue() const { return false; }
175 /// Override from Constant class.
176 virtual void destroyConstant();
178 /// isDeclaration - Return true if the primary definition of this global
179 /// value is outside of the current translation unit...
180 virtual bool isDeclaration() const = 0;
182 /// removeFromParent - This method unlinks 'this' from the containing module,
183 /// but does not delete it.
184 virtual void removeFromParent() = 0;
186 /// eraseFromParent - This method unlinks 'this' from the containing module
188 virtual void eraseFromParent() = 0;
190 /// getParent - Get the module that this global value is contained inside
192 inline Module *getParent() { return Parent; }
193 inline const Module *getParent() const { return Parent; }
195 /// removeDeadConstantUsers - If there are any dead constant users dangling
196 /// off of this global value, remove them. This method is useful for clients
197 /// that want to check to see if a global is unused, but don't want to deal
198 /// with potentially dead constants hanging off of the globals.
199 void removeDeadConstantUsers() const;
201 // Methods for support type inquiry through isa, cast, and dyn_cast:
202 static inline bool classof(const GlobalValue *) { return true; }
203 static inline bool classof(const Value *V) {
204 return V->getValueID() == Value::FunctionVal ||
205 V->getValueID() == Value::GlobalVariableVal ||
206 V->getValueID() == Value::GlobalAliasVal;
210 } // End llvm namespace