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_IR_GLOBALVALUE_H
19 #define LLVM_IR_GLOBALVALUE_H
21 #include "llvm/IR/Constant.h"
22 #include "llvm/IR/DerivedTypes.h"
29 class GlobalValue : public Constant {
30 GlobalValue(const GlobalValue &) LLVM_DELETED_FUNCTION;
32 /// @brief An enumeration for the kinds of linkage for global values.
34 ExternalLinkage = 0,///< Externally visible function
35 AvailableExternallyLinkage, ///< Available for inspection, not emission.
36 LinkOnceAnyLinkage, ///< Keep one copy of function when linking (inline)
37 LinkOnceODRLinkage, ///< Same, but only replaced by something equivalent.
38 LinkOnceODRAutoHideLinkage, ///< Like LinkOnceODRLinkage but addr not taken.
39 WeakAnyLinkage, ///< Keep one copy of named function when linking (weak)
40 WeakODRLinkage, ///< Same, but only replaced by something equivalent.
41 AppendingLinkage, ///< Special purpose, only applies to global arrays
42 InternalLinkage, ///< Rename collisions when linking (static functions).
43 PrivateLinkage, ///< Like Internal, but omit from symbol table.
44 LinkerPrivateLinkage, ///< Like Private, but linker removes.
45 LinkerPrivateWeakLinkage, ///< Like LinkerPrivate, but weak.
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(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps,
61 LinkageTypes linkage, const Twine &Name)
62 : Constant(ty, vty, Ops, NumOps), Linkage(linkage),
63 Visibility(DefaultVisibility), Alignment(0), UnnamedAddr(0), Parent(0) {
67 // Note: VC++ treats enums as signed, so an extra bit is required to prevent
68 // Linkage and Visibility from turning into negative values.
69 LinkageTypes Linkage : 5; // The linkage of this global
70 unsigned Visibility : 2; // The visibility style of this global
71 unsigned Alignment : 16; // Alignment of this symbol, must be power of two
72 unsigned UnnamedAddr : 1; // This value's address is not significant
73 Module *Parent; // The containing module.
74 std::string Section; // Section to emit this into, empty mean default
77 removeDeadConstantUsers(); // remove any dead constants using this.
80 unsigned getAlignment() const {
81 return (1u << Alignment) >> 1;
83 void setAlignment(unsigned Align);
85 bool hasUnnamedAddr() const { return UnnamedAddr; }
86 void setUnnamedAddr(bool Val) { UnnamedAddr = Val; }
88 VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
89 bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; }
90 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
91 bool hasProtectedVisibility() const {
92 return Visibility == ProtectedVisibility;
94 void setVisibility(VisibilityTypes V) { Visibility = V; }
96 bool hasSection() const { return !Section.empty(); }
97 const std::string &getSection() const { return Section; }
98 void setSection(StringRef S) { Section = S; }
100 /// If the usage is empty (except transitively dead constants), then this
101 /// global value can be safely deleted since the destructor will
102 /// delete the dead constants as well.
103 /// @brief Determine if the usage of this global value is empty except
104 /// for transitively dead constants.
105 bool use_empty_except_constants();
107 /// getType - Global values are always pointers.
108 inline PointerType *getType() const {
109 return cast<PointerType>(User::getType());
112 static LinkageTypes getLinkOnceLinkage(bool ODR) {
113 return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;
115 static LinkageTypes getWeakLinkage(bool ODR) {
116 return ODR ? WeakODRLinkage : WeakAnyLinkage;
119 static bool isExternalLinkage(LinkageTypes Linkage) {
120 return Linkage == ExternalLinkage;
122 static bool isAvailableExternallyLinkage(LinkageTypes Linkage) {
123 return Linkage == AvailableExternallyLinkage;
125 static bool isLinkOnceLinkage(LinkageTypes Linkage) {
126 return Linkage == LinkOnceAnyLinkage ||
127 Linkage == LinkOnceODRLinkage ||
128 Linkage == LinkOnceODRAutoHideLinkage;
130 static bool isLinkOnceODRAutoHideLinkage(LinkageTypes Linkage) {
131 return Linkage == LinkOnceODRAutoHideLinkage;
133 static bool isWeakLinkage(LinkageTypes Linkage) {
134 return Linkage == WeakAnyLinkage || Linkage == WeakODRLinkage;
136 static bool isAppendingLinkage(LinkageTypes Linkage) {
137 return Linkage == AppendingLinkage;
139 static bool isInternalLinkage(LinkageTypes Linkage) {
140 return Linkage == InternalLinkage;
142 static bool isPrivateLinkage(LinkageTypes Linkage) {
143 return Linkage == PrivateLinkage;
145 static bool isLinkerPrivateLinkage(LinkageTypes Linkage) {
146 return Linkage == LinkerPrivateLinkage;
148 static bool isLinkerPrivateWeakLinkage(LinkageTypes Linkage) {
149 return Linkage == LinkerPrivateWeakLinkage;
151 static bool isLocalLinkage(LinkageTypes Linkage) {
152 return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage) ||
153 isLinkerPrivateLinkage(Linkage) || isLinkerPrivateWeakLinkage(Linkage);
155 static bool isDLLImportLinkage(LinkageTypes Linkage) {
156 return Linkage == DLLImportLinkage;
158 static bool isDLLExportLinkage(LinkageTypes Linkage) {
159 return Linkage == DLLExportLinkage;
161 static bool isExternalWeakLinkage(LinkageTypes Linkage) {
162 return Linkage == ExternalWeakLinkage;
164 static bool isCommonLinkage(LinkageTypes Linkage) {
165 return Linkage == CommonLinkage;
168 /// isDiscardableIfUnused - Whether the definition of this global may be
169 /// discarded if it is not used in its compilation unit.
170 static bool isDiscardableIfUnused(LinkageTypes Linkage) {
171 return isLinkOnceLinkage(Linkage) || isLocalLinkage(Linkage);
174 /// mayBeOverridden - Whether the definition of this global may be replaced
175 /// by something non-equivalent at link time. For example, if a function has
176 /// weak linkage then the code defining it may be replaced by different code.
177 static bool mayBeOverridden(LinkageTypes Linkage) {
178 return Linkage == WeakAnyLinkage ||
179 Linkage == LinkOnceAnyLinkage ||
180 Linkage == CommonLinkage ||
181 Linkage == ExternalWeakLinkage ||
182 Linkage == LinkerPrivateWeakLinkage;
185 /// isWeakForLinker - Whether the definition of this global may be replaced at
186 /// link time. NB: Using this method outside of the code generators is almost
187 /// always a mistake: when working at the IR level use mayBeOverridden instead
188 /// as it knows about ODR semantics.
189 static bool isWeakForLinker(LinkageTypes Linkage) {
190 return Linkage == AvailableExternallyLinkage ||
191 Linkage == WeakAnyLinkage ||
192 Linkage == WeakODRLinkage ||
193 Linkage == LinkOnceAnyLinkage ||
194 Linkage == LinkOnceODRLinkage ||
195 Linkage == LinkOnceODRAutoHideLinkage ||
196 Linkage == CommonLinkage ||
197 Linkage == ExternalWeakLinkage ||
198 Linkage == LinkerPrivateWeakLinkage;
201 bool hasExternalLinkage() const { return isExternalLinkage(Linkage); }
202 bool hasAvailableExternallyLinkage() const {
203 return isAvailableExternallyLinkage(Linkage);
205 bool hasLinkOnceLinkage() const {
206 return isLinkOnceLinkage(Linkage);
208 bool hasLinkOnceODRAutoHideLinkage() const {
209 return isLinkOnceODRAutoHideLinkage(Linkage);
211 bool hasWeakLinkage() const {
212 return isWeakLinkage(Linkage);
214 bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage); }
215 bool hasInternalLinkage() const { return isInternalLinkage(Linkage); }
216 bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); }
217 bool hasLinkerPrivateLinkage() const { return isLinkerPrivateLinkage(Linkage); }
218 bool hasLinkerPrivateWeakLinkage() const {
219 return isLinkerPrivateWeakLinkage(Linkage);
221 bool hasLocalLinkage() const { return isLocalLinkage(Linkage); }
222 bool hasDLLImportLinkage() const { return isDLLImportLinkage(Linkage); }
223 bool hasDLLExportLinkage() const { return isDLLExportLinkage(Linkage); }
224 bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); }
225 bool hasCommonLinkage() const { return isCommonLinkage(Linkage); }
227 void setLinkage(LinkageTypes LT) { Linkage = LT; }
228 LinkageTypes getLinkage() const { return Linkage; }
230 bool isDiscardableIfUnused() const {
231 return isDiscardableIfUnused(Linkage);
234 bool mayBeOverridden() const { return mayBeOverridden(Linkage); }
236 bool isWeakForLinker() const { return isWeakForLinker(Linkage); }
238 /// copyAttributesFrom - copy all additional attributes (those not needed to
239 /// create a GlobalValue) from the GlobalValue Src to this one.
240 virtual void copyAttributesFrom(const GlobalValue *Src);
242 /// getRealLinkageName - If special LLVM prefix that is used to inform the asm
243 /// printer to not emit usual symbol prefix before the symbol name is used
244 /// then return linkage name after skipping this special LLVM prefix.
245 static StringRef getRealLinkageName(StringRef Name) {
246 if (!Name.empty() && Name[0] == '\1')
247 return Name.substr(1);
251 /// @name Materialization
252 /// Materialization is used to construct functions only as they're needed. This
253 /// is useful to reduce memory usage in LLVM or parsing work done by the
254 /// BitcodeReader to load the Module.
257 /// isMaterializable - If this function's Module is being lazily streamed in
258 /// functions from disk or some other source, this method can be used to check
259 /// to see if the function has been read in yet or not.
260 bool isMaterializable() const;
262 /// isDematerializable - Returns true if this function was loaded from a
263 /// GVMaterializer that's still attached to its Module and that knows how to
264 /// dematerialize the function.
265 bool isDematerializable() const;
267 /// Materialize - make sure this GlobalValue is fully read. If the module is
268 /// corrupt, this returns true and fills in the optional string with
269 /// information about the problem. If successful, this returns false.
270 bool Materialize(std::string *ErrInfo = 0);
272 /// Dematerialize - If this GlobalValue is read in, and if the GVMaterializer
273 /// supports it, release the memory for the function, and set it up to be
274 /// materialized lazily. If !isDematerializable(), this method is a noop.
275 void Dematerialize();
279 /// Override from Constant class.
280 virtual void destroyConstant();
282 /// isDeclaration - Return true if the primary definition of this global
283 /// value is outside of the current translation unit.
284 bool isDeclaration() const;
286 /// removeFromParent - This method unlinks 'this' from the containing module,
287 /// but does not delete it.
288 virtual void removeFromParent() = 0;
290 /// eraseFromParent - This method unlinks 'this' from the containing module
292 virtual void eraseFromParent() = 0;
294 /// getParent - Get the module that this global value is contained inside
296 inline Module *getParent() { return Parent; }
297 inline const Module *getParent() const { return Parent; }
299 // Methods for support type inquiry through isa, cast, and dyn_cast:
300 static inline bool classof(const Value *V) {
301 return V->getValueID() == Value::FunctionVal ||
302 V->getValueID() == Value::GlobalVariableVal ||
303 V->getValueID() == Value::GlobalAliasVal;
307 } // End llvm namespace