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