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 WeakAnyLinkage, ///< Keep one copy of named function when linking (weak)
39 WeakODRLinkage, ///< Same, but only replaced by something equivalent.
40 AppendingLinkage, ///< Special purpose, only applies to global arrays
41 InternalLinkage, ///< Rename collisions when linking (static functions).
42 PrivateLinkage, ///< Like Internal, but omit from symbol table.
43 ExternalWeakLinkage,///< ExternalWeak linkage description.
44 CommonLinkage ///< Tentative definitions.
47 /// @brief An enumeration for the kinds of visibility of global values.
48 enum VisibilityTypes {
49 DefaultVisibility = 0, ///< The GV is visible
50 HiddenVisibility, ///< The GV is hidden
51 ProtectedVisibility ///< The GV is protected
54 /// @brief Storage classes of global values for PE targets.
55 enum DLLStorageClassTypes {
56 DefaultStorageClass = 0,
57 DLLImportStorageClass = 1, ///< Function to be imported from DLL
58 DLLExportStorageClass = 2 ///< Function to be accessible from DLL.
62 GlobalValue(Type *Ty, ValueTy VTy, Use *Ops, unsigned NumOps,
63 LinkageTypes Linkage, const Twine &Name)
64 : Constant(Ty, VTy, Ops, NumOps), Linkage(Linkage),
65 Visibility(DefaultVisibility), UnnamedAddr(0),
66 DllStorageClass(DefaultStorageClass), Parent(nullptr) {
70 // Note: VC++ treats enums as signed, so an extra bit is required to prevent
71 // Linkage and Visibility from turning into negative values.
72 LinkageTypes Linkage : 5; // The linkage of this global
73 unsigned Visibility : 2; // The visibility style of this global
74 unsigned UnnamedAddr : 1; // This value's address is not significant
75 unsigned DllStorageClass : 2; // DLL storage class
78 // Give subclasses access to what otherwise would be wasted padding.
79 // (22 + 2 + 1 + 2 + 5) == 32.
80 unsigned SubClassData : 22;
82 unsigned getGlobalValueSubClassData() const {
85 void setGlobalValueSubClassData(unsigned V) {
86 assert(V < (1 << 22) && "It will not fit");
90 Module *Parent; // The containing module.
93 removeDeadConstantUsers(); // remove any dead constants using this.
96 unsigned getAlignment() const;
98 bool hasUnnamedAddr() const { return UnnamedAddr; }
99 void setUnnamedAddr(bool Val) { UnnamedAddr = Val; }
101 VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
102 bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; }
103 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
104 bool hasProtectedVisibility() const {
105 return Visibility == ProtectedVisibility;
107 void setVisibility(VisibilityTypes V) {
108 assert((!hasLocalLinkage() || V == DefaultVisibility) &&
109 "local linkage requires default visibility");
113 DLLStorageClassTypes getDLLStorageClass() const {
114 return DLLStorageClassTypes(DllStorageClass);
116 bool hasDLLImportStorageClass() const {
117 return DllStorageClass == DLLImportStorageClass;
119 bool hasDLLExportStorageClass() const {
120 return DllStorageClass == DLLExportStorageClass;
122 void setDLLStorageClass(DLLStorageClassTypes C) { DllStorageClass = C; }
124 bool hasSection() const { return !getSection().empty(); }
125 const std::string &getSection() const;
127 /// Global values are always pointers.
128 inline PointerType *getType() const {
129 return cast<PointerType>(User::getType());
132 static LinkageTypes getLinkOnceLinkage(bool ODR) {
133 return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;
135 static LinkageTypes getWeakLinkage(bool ODR) {
136 return ODR ? WeakODRLinkage : WeakAnyLinkage;
139 static bool isExternalLinkage(LinkageTypes Linkage) {
140 return Linkage == ExternalLinkage;
142 static bool isAvailableExternallyLinkage(LinkageTypes Linkage) {
143 return Linkage == AvailableExternallyLinkage;
145 static bool isLinkOnceLinkage(LinkageTypes Linkage) {
146 return Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage;
148 static bool isWeakAnyLinkage(LinkageTypes Linkage) {
149 return Linkage == WeakAnyLinkage;
151 static bool isWeakODRLinkage(LinkageTypes Linkage) {
152 return Linkage == WeakODRLinkage;
154 static bool isWeakLinkage(LinkageTypes Linkage) {
155 return isWeakAnyLinkage(Linkage) || isWeakODRLinkage(Linkage);
157 static bool isAppendingLinkage(LinkageTypes Linkage) {
158 return Linkage == AppendingLinkage;
160 static bool isInternalLinkage(LinkageTypes Linkage) {
161 return Linkage == InternalLinkage;
163 static bool isPrivateLinkage(LinkageTypes Linkage) {
164 return Linkage == PrivateLinkage;
166 static bool isLocalLinkage(LinkageTypes Linkage) {
167 return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage);
169 static bool isExternalWeakLinkage(LinkageTypes Linkage) {
170 return Linkage == ExternalWeakLinkage;
172 static bool isCommonLinkage(LinkageTypes Linkage) {
173 return Linkage == CommonLinkage;
176 /// Whether the definition of this global may be discarded if it is not used
177 /// in its compilation unit.
178 static bool isDiscardableIfUnused(LinkageTypes Linkage) {
179 return isLinkOnceLinkage(Linkage) || isLocalLinkage(Linkage);
182 /// Whether the definition of this global may be replaced by something
183 /// non-equivalent at link time. For example, if a function has weak linkage
184 /// then the code defining it may be replaced by different code.
185 static bool mayBeOverridden(LinkageTypes Linkage) {
186 return Linkage == WeakAnyLinkage || Linkage == LinkOnceAnyLinkage ||
187 Linkage == CommonLinkage || Linkage == ExternalWeakLinkage;
190 /// Whether the definition of this global may be replaced at link time. NB:
191 /// Using this method outside of the code generators is almost always a
192 /// mistake: when working at the IR level use mayBeOverridden instead as it
193 /// knows about ODR semantics.
194 static bool isWeakForLinker(LinkageTypes Linkage) {
195 return Linkage == AvailableExternallyLinkage || Linkage == WeakAnyLinkage ||
196 Linkage == WeakODRLinkage || Linkage == LinkOnceAnyLinkage ||
197 Linkage == LinkOnceODRLinkage || Linkage == CommonLinkage ||
198 Linkage == ExternalWeakLinkage;
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 hasWeakLinkage() const {
209 return isWeakLinkage(Linkage);
211 bool hasWeakAnyLinkage() const {
212 return isWeakAnyLinkage(Linkage);
214 bool hasWeakODRLinkage() const {
215 return isWeakODRLinkage(Linkage);
217 bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage); }
218 bool hasInternalLinkage() const { return isInternalLinkage(Linkage); }
219 bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); }
220 bool hasLocalLinkage() const { return isLocalLinkage(Linkage); }
221 bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); }
222 bool hasCommonLinkage() const { return isCommonLinkage(Linkage); }
224 void setLinkage(LinkageTypes LT) {
225 if (isLocalLinkage(LT))
226 Visibility = DefaultVisibility;
229 LinkageTypes getLinkage() const { return Linkage; }
231 bool isDiscardableIfUnused() const {
232 return isDiscardableIfUnused(Linkage);
235 bool mayBeOverridden() const { return mayBeOverridden(Linkage); }
237 bool isWeakForLinker() const { return isWeakForLinker(Linkage); }
239 /// Copy all additional attributes (those not needed to create a GlobalValue)
240 /// from the GlobalValue Src to this one.
241 virtual void copyAttributesFrom(const GlobalValue *Src);
243 /// If special LLVM prefix that is used to inform the asm printer to not emit
244 /// usual symbol prefix before the symbol name is used then return linkage
245 /// name after skipping this special LLVM prefix.
246 static StringRef getRealLinkageName(StringRef Name) {
247 if (!Name.empty() && Name[0] == '\1')
248 return Name.substr(1);
252 /// @name Materialization
253 /// Materialization is used to construct functions only as they're needed. This
254 /// is useful to reduce memory usage in LLVM or parsing work done by the
255 /// BitcodeReader to load the Module.
258 /// If this function's Module is being lazily streamed in functions from disk
259 /// or some other source, this method can be used to check to see if the
260 /// function has been read in yet or not.
261 bool isMaterializable() const;
263 /// Returns true if this function was loaded from a GVMaterializer that's
264 /// still attached to its Module and that knows how to dematerialize the
266 bool isDematerializable() const;
268 /// Make sure this GlobalValue is fully read. If the module is corrupt, this
269 /// returns true and fills in the optional string with information about the
270 /// problem. If successful, this returns false.
271 bool Materialize(std::string *ErrInfo = nullptr);
273 /// If this GlobalValue is read in, and if the GVMaterializer supports it,
274 /// release the memory for the function, and set it up to be materialized
275 /// lazily. If !isDematerializable(), this method is a noop.
276 void Dematerialize();
280 /// Override from Constant class.
281 void destroyConstant() override;
283 /// Return true if the primary definition of this global value is outside of
284 /// the current translation unit.
285 bool isDeclaration() const;
287 /// This method unlinks 'this' from the containing module, but does not delete
289 virtual void removeFromParent() = 0;
291 /// This method unlinks 'this' from the containing module and deletes it.
292 virtual void eraseFromParent() = 0;
294 /// Get the module that this global value is contained inside of...
295 inline Module *getParent() { return Parent; }
296 inline const Module *getParent() const { return Parent; }
298 const DataLayout *getDataLayout() const;
300 // Methods for support type inquiry through isa, cast, and dyn_cast:
301 static inline bool classof(const Value *V) {
302 return V->getValueID() == Value::FunctionVal ||
303 V->getValueID() == Value::GlobalVariableVal ||
304 V->getValueID() == Value::GlobalAliasVal;
308 } // End llvm namespace