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 LinkerPrivateWeakDefAutoLinkage, ///< Like LinkerPrivateWeak, but possibly
46 DLLImportLinkage, ///< Function to be imported from DLL
47 DLLExportLinkage, ///< Function to be accessible from DLL.
48 ExternalWeakLinkage,///< ExternalWeak linkage description.
49 CommonLinkage ///< Tentative definitions.
52 /// @brief An enumeration for the kinds of visibility of global values.
53 enum VisibilityTypes {
54 DefaultVisibility = 0, ///< The GV is visible
55 HiddenVisibility, ///< The GV is hidden
56 ProtectedVisibility ///< The GV is protected
60 GlobalValue(const Type *ty, ValueTy vty, Use *Ops, unsigned NumOps,
61 LinkageTypes linkage, const Twine &Name)
62 : Constant(ty, vty, Ops, NumOps), Parent(0),
63 Linkage(linkage), Visibility(DefaultVisibility), Alignment(0) {
68 // Note: VC++ treats enums as signed, so an extra bit is required to prevent
69 // Linkage and Visibility from turning into negative values.
70 LinkageTypes Linkage : 5; // The linkage of this global
71 unsigned Visibility : 2; // The visibility style of this global
72 unsigned Alignment : 16; // Alignment of this symbol, must be power of two
73 std::string Section; // Section to emit this into, empty mean default
76 removeDeadConstantUsers(); // remove any dead constants using this.
79 unsigned getAlignment() const {
80 return (1u << Alignment) >> 1;
82 void setAlignment(unsigned Align);
84 VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
85 bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; }
86 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
87 bool hasProtectedVisibility() const {
88 return Visibility == ProtectedVisibility;
90 void setVisibility(VisibilityTypes V) { Visibility = V; }
92 bool hasSection() const { return !Section.empty(); }
93 const std::string &getSection() const { return Section; }
94 void setSection(StringRef S) { Section = S; }
96 /// If the usage is empty (except transitively dead constants), then this
97 /// global value can be safely deleted since the destructor will
98 /// delete the dead constants as well.
99 /// @brief Determine if the usage of this global value is empty except
100 /// for transitively dead constants.
101 bool use_empty_except_constants();
103 /// getType - Global values are always pointers.
104 inline const PointerType *getType() const {
105 return reinterpret_cast<const PointerType*>(User::getType());
108 static LinkageTypes getLinkOnceLinkage(bool ODR) {
109 return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;
111 static LinkageTypes getWeakLinkage(bool ODR) {
112 return ODR ? WeakODRLinkage : WeakAnyLinkage;
115 static bool isExternalLinkage(LinkageTypes Linkage) {
116 return Linkage == ExternalLinkage;
118 static bool isAvailableExternallyLinkage(LinkageTypes Linkage) {
119 return Linkage == AvailableExternallyLinkage;
121 static bool isLinkOnceLinkage(LinkageTypes Linkage) {
122 return Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage;
124 static bool isWeakLinkage(LinkageTypes Linkage) {
125 return Linkage == WeakAnyLinkage || Linkage == WeakODRLinkage;
127 static bool isAppendingLinkage(LinkageTypes Linkage) {
128 return Linkage == AppendingLinkage;
130 static bool isInternalLinkage(LinkageTypes Linkage) {
131 return Linkage == InternalLinkage;
133 static bool isPrivateLinkage(LinkageTypes Linkage) {
134 return Linkage == PrivateLinkage;
136 static bool isLinkerPrivateLinkage(LinkageTypes Linkage) {
137 return Linkage == LinkerPrivateLinkage;
139 static bool isLinkerPrivateWeakLinkage(LinkageTypes Linkage) {
140 return Linkage == LinkerPrivateWeakLinkage;
142 static bool isLinkerPrivateWeakDefAutoLinkage(LinkageTypes Linkage) {
143 return Linkage == LinkerPrivateWeakDefAutoLinkage;
145 static bool isLocalLinkage(LinkageTypes Linkage) {
146 return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage) ||
147 isLinkerPrivateLinkage(Linkage) || isLinkerPrivateWeakLinkage(Linkage) ||
148 isLinkerPrivateWeakDefAutoLinkage(Linkage);
150 static bool isDLLImportLinkage(LinkageTypes Linkage) {
151 return Linkage == DLLImportLinkage;
153 static bool isDLLExportLinkage(LinkageTypes Linkage) {
154 return Linkage == DLLExportLinkage;
156 static bool isExternalWeakLinkage(LinkageTypes Linkage) {
157 return Linkage == ExternalWeakLinkage;
159 static bool isCommonLinkage(LinkageTypes Linkage) {
160 return Linkage == CommonLinkage;
163 /// mayBeOverridden - Whether the definition of this global may be replaced
164 /// by something non-equivalent at link time. For example, if a function has
165 /// weak linkage then the code defining it may be replaced by different code.
166 static bool mayBeOverridden(LinkageTypes Linkage) {
167 return Linkage == WeakAnyLinkage ||
168 Linkage == LinkOnceAnyLinkage ||
169 Linkage == CommonLinkage ||
170 Linkage == ExternalWeakLinkage ||
171 Linkage == LinkerPrivateWeakLinkage ||
172 Linkage == LinkerPrivateWeakDefAutoLinkage;
175 /// isWeakForLinker - Whether the definition of this global may be replaced at
177 static bool isWeakForLinker(LinkageTypes Linkage) {
178 return Linkage == AvailableExternallyLinkage ||
179 Linkage == WeakAnyLinkage ||
180 Linkage == WeakODRLinkage ||
181 Linkage == LinkOnceAnyLinkage ||
182 Linkage == LinkOnceODRLinkage ||
183 Linkage == CommonLinkage ||
184 Linkage == ExternalWeakLinkage ||
185 Linkage == LinkerPrivateWeakLinkage ||
186 Linkage == LinkerPrivateWeakDefAutoLinkage;
189 bool hasExternalLinkage() const { return isExternalLinkage(Linkage); }
190 bool hasAvailableExternallyLinkage() const {
191 return isAvailableExternallyLinkage(Linkage);
193 bool hasLinkOnceLinkage() const {
194 return isLinkOnceLinkage(Linkage);
196 bool hasWeakLinkage() const {
197 return isWeakLinkage(Linkage);
199 bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage); }
200 bool hasInternalLinkage() const { return isInternalLinkage(Linkage); }
201 bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); }
202 bool hasLinkerPrivateLinkage() const { return isLinkerPrivateLinkage(Linkage); }
203 bool hasLinkerPrivateWeakLinkage() const {
204 return isLinkerPrivateWeakLinkage(Linkage);
206 bool hasLinkerPrivateWeakDefAutoLinkage() const {
207 return isLinkerPrivateWeakDefAutoLinkage(Linkage);
209 bool hasLocalLinkage() const { return isLocalLinkage(Linkage); }
210 bool hasDLLImportLinkage() const { return isDLLImportLinkage(Linkage); }
211 bool hasDLLExportLinkage() const { return isDLLExportLinkage(Linkage); }
212 bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); }
213 bool hasCommonLinkage() const { return isCommonLinkage(Linkage); }
215 void setLinkage(LinkageTypes LT) { Linkage = LT; }
216 LinkageTypes getLinkage() const { return Linkage; }
218 bool mayBeOverridden() const { return mayBeOverridden(Linkage); }
220 bool isWeakForLinker() const { return isWeakForLinker(Linkage); }
222 /// copyAttributesFrom - copy all additional attributes (those not needed to
223 /// create a GlobalValue) from the GlobalValue Src to this one.
224 virtual void copyAttributesFrom(const GlobalValue *Src);
226 /// @name Materialization
227 /// Materialization is used to construct functions only as they're needed. This
228 /// is useful to reduce memory usage in LLVM or parsing work done by the
229 /// BitcodeReader to load the Module.
232 /// isMaterializable - If this function's Module is being lazily streamed in
233 /// functions from disk or some other source, this method can be used to check
234 /// to see if the function has been read in yet or not.
235 bool isMaterializable() const;
237 /// isDematerializable - Returns true if this function was loaded from a
238 /// GVMaterializer that's still attached to its Module and that knows how to
239 /// dematerialize the function.
240 bool isDematerializable() const;
242 /// Materialize - make sure this GlobalValue is fully read. If the module is
243 /// corrupt, this returns true and fills in the optional string with
244 /// information about the problem. If successful, this returns false.
245 bool Materialize(std::string *ErrInfo = 0);
247 /// Dematerialize - If this GlobalValue is read in, and if the GVMaterializer
248 /// supports it, release the memory for the function, and set it up to be
249 /// materialized lazily. If !isDematerializable(), this method is a noop.
250 void Dematerialize();
254 /// Override from Constant class. No GlobalValue's are null values so this
255 /// always returns false.
256 virtual bool isNullValue() const { return false; }
258 /// Override from Constant class.
259 virtual void destroyConstant();
261 /// isDeclaration - Return true if the primary definition of this global
262 /// value is outside of the current translation unit...
263 virtual bool isDeclaration() const = 0;
265 /// removeFromParent - This method unlinks 'this' from the containing module,
266 /// but does not delete it.
267 virtual void removeFromParent() = 0;
269 /// eraseFromParent - This method unlinks 'this' from the containing module
271 virtual void eraseFromParent() = 0;
273 /// getParent - Get the module that this global value is contained inside
275 inline Module *getParent() { return Parent; }
276 inline const Module *getParent() const { return Parent; }
278 /// removeDeadConstantUsers - If there are any dead constant users dangling
279 /// off of this global value, remove them. This method is useful for clients
280 /// that want to check to see if a global is unused, but don't want to deal
281 /// with potentially dead constants hanging off of the globals.
282 void removeDeadConstantUsers() const;
284 // Methods for support type inquiry through isa, cast, and dyn_cast:
285 static inline bool classof(const GlobalValue *) { return true; }
286 static inline bool classof(const Value *V) {
287 return V->getValueID() == Value::FunctionVal ||
288 V->getValueID() == Value::GlobalVariableVal ||
289 V->getValueID() == Value::GlobalAliasVal;
293 } // End llvm namespace