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 LinkerPrivateWeakLinkage, ///< Like LinkerPrivate, but weak.
44 DLLImportLinkage, ///< Function to be imported from DLL
45 DLLExportLinkage, ///< Function to be accessible from DLL.
46 ExternalWeakLinkage,///< ExternalWeak linkage description.
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 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 static bool isExternalLinkage(LinkageTypes Linkage) {
115 return Linkage == ExternalLinkage;
117 static bool isAvailableExternallyLinkage(LinkageTypes Linkage) {
118 return Linkage == AvailableExternallyLinkage;
120 static bool isLinkOnceLinkage(LinkageTypes Linkage) {
121 return Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage;
123 static bool isWeakLinkage(LinkageTypes Linkage) {
124 return Linkage == WeakAnyLinkage || Linkage == WeakODRLinkage;
126 static bool isAppendingLinkage(LinkageTypes Linkage) {
127 return Linkage == AppendingLinkage;
129 static bool isInternalLinkage(LinkageTypes Linkage) {
130 return Linkage == InternalLinkage;
132 static bool isPrivateLinkage(LinkageTypes Linkage) {
133 return Linkage == PrivateLinkage;
135 static bool isLinkerPrivateLinkage(LinkageTypes Linkage) {
136 return Linkage == LinkerPrivateLinkage;
138 static bool isLinkerPrivateWeakLinkage(LinkageTypes Linkage) {
139 return Linkage == LinkerPrivateWeakLinkage;
141 static bool isLocalLinkage(LinkageTypes Linkage) {
142 return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage) ||
143 isLinkerPrivateLinkage(Linkage) || isLinkerPrivateWeakLinkage(Linkage);
145 static bool isDLLImportLinkage(LinkageTypes Linkage) {
146 return Linkage == DLLImportLinkage;
148 static bool isDLLExportLinkage(LinkageTypes Linkage) {
149 return Linkage == DLLExportLinkage;
151 static bool isExternalWeakLinkage(LinkageTypes Linkage) {
152 return Linkage == ExternalWeakLinkage;
154 static bool isCommonLinkage(LinkageTypes Linkage) {
155 return Linkage == CommonLinkage;
158 /// mayBeOverridden - Whether the definition of this global may be replaced
159 /// by something non-equivalent at link time. For example, if a function has
160 /// weak linkage then the code defining it may be replaced by different code.
161 static bool mayBeOverridden(LinkageTypes Linkage) {
162 return (Linkage == WeakAnyLinkage ||
163 Linkage == LinkOnceAnyLinkage ||
164 Linkage == CommonLinkage ||
165 Linkage == ExternalWeakLinkage ||
166 Linkage == LinkerPrivateWeakLinkage);
169 /// isWeakForLinker - Whether the definition of this global may be replaced at
171 static bool isWeakForLinker(LinkageTypes Linkage) {
172 return (Linkage == AvailableExternallyLinkage ||
173 Linkage == WeakAnyLinkage ||
174 Linkage == WeakODRLinkage ||
175 Linkage == LinkOnceAnyLinkage ||
176 Linkage == LinkOnceODRLinkage ||
177 Linkage == CommonLinkage ||
178 Linkage == ExternalWeakLinkage ||
179 Linkage == LinkerPrivateWeakLinkage);
182 bool hasExternalLinkage() const { return isExternalLinkage(Linkage); }
183 bool hasAvailableExternallyLinkage() const {
184 return isAvailableExternallyLinkage(Linkage);
186 bool hasLinkOnceLinkage() const {
187 return isLinkOnceLinkage(Linkage);
189 bool hasWeakLinkage() const {
190 return isWeakLinkage(Linkage);
192 bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage); }
193 bool hasInternalLinkage() const { return isInternalLinkage(Linkage); }
194 bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); }
195 bool hasLinkerPrivateLinkage() const { return isLinkerPrivateLinkage(Linkage); }
196 bool hasLinkerPrivateWeakLinkage() const {
197 return isLinkerPrivateWeakLinkage(Linkage);
199 bool hasLocalLinkage() const { return isLocalLinkage(Linkage); }
200 bool hasDLLImportLinkage() const { return isDLLImportLinkage(Linkage); }
201 bool hasDLLExportLinkage() const { return isDLLExportLinkage(Linkage); }
202 bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); }
203 bool hasCommonLinkage() const { return isCommonLinkage(Linkage); }
205 void setLinkage(LinkageTypes LT) { Linkage = LT; }
206 LinkageTypes getLinkage() const { return Linkage; }
208 bool mayBeOverridden() const { return mayBeOverridden(Linkage); }
210 bool isWeakForLinker() const { return isWeakForLinker(Linkage); }
212 /// copyAttributesFrom - copy all additional attributes (those not needed to
213 /// create a GlobalValue) from the GlobalValue Src to this one.
214 virtual void copyAttributesFrom(const GlobalValue *Src);
216 /// @name Materialization
217 /// Materialization is used to construct functions only as they're needed. This
218 /// is useful to reduce memory usage in LLVM or parsing work done by the
219 /// BitcodeReader to load the Module.
222 /// isMaterializable - If this function's Module is being lazily streamed in
223 /// functions from disk or some other source, this method can be used to check
224 /// to see if the function has been read in yet or not.
225 bool isMaterializable() const;
227 /// isDematerializable - Returns true if this function was loaded from a
228 /// GVMaterializer that's still attached to its Module and that knows how to
229 /// dematerialize the function.
230 bool isDematerializable() const;
232 /// Materialize - make sure this GlobalValue is fully read. If the module is
233 /// corrupt, this returns true and fills in the optional string with
234 /// information about the problem. If successful, this returns false.
235 bool Materialize(std::string *ErrInfo = 0);
237 /// Dematerialize - If this GlobalValue is read in, and if the GVMaterializer
238 /// supports it, release the memory for the function, and set it up to be
239 /// materialized lazily. If !isDematerializable(), this method is a noop.
240 void Dematerialize();
244 /// Override from Constant class. No GlobalValue's are null values so this
245 /// always returns false.
246 virtual bool isNullValue() const { return false; }
248 /// Override from Constant class.
249 virtual void destroyConstant();
251 /// isDeclaration - Return true if the primary definition of this global
252 /// value is outside of the current translation unit...
253 virtual bool isDeclaration() const = 0;
255 /// removeFromParent - This method unlinks 'this' from the containing module,
256 /// but does not delete it.
257 virtual void removeFromParent() = 0;
259 /// eraseFromParent - This method unlinks 'this' from the containing module
261 virtual void eraseFromParent() = 0;
263 /// getParent - Get the module that this global value is contained inside
265 inline Module *getParent() { return Parent; }
266 inline const Module *getParent() const { return Parent; }
268 /// removeDeadConstantUsers - If there are any dead constant users dangling
269 /// off of this global value, remove them. This method is useful for clients
270 /// that want to check to see if a global is unused, but don't want to deal
271 /// with potentially dead constants hanging off of the globals.
272 void removeDeadConstantUsers() const;
274 // Methods for support type inquiry through isa, cast, and dyn_cast:
275 static inline bool classof(const GlobalValue *) { return true; }
276 static inline bool classof(const Value *V) {
277 return V->getValueID() == Value::FunctionVal ||
278 V->getValueID() == Value::GlobalVariableVal ||
279 V->getValueID() == Value::GlobalAliasVal;
283 } // End llvm namespace