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), Alignment(0), 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 Alignment : 16; // Alignment of this symbol, must be power of two
75 unsigned UnnamedAddr : 1; // This value's address is not significant
76 unsigned DllStorageClass : 2; // DLL storage class
77 Module *Parent; // The containing module.
78 std::string Section; // Section to emit this into, empty mean default
81 removeDeadConstantUsers(); // remove any dead constants using this.
84 unsigned getAlignment() const;
85 void setAlignment(unsigned Align);
87 bool hasUnnamedAddr() const { return UnnamedAddr; }
88 void setUnnamedAddr(bool Val) { UnnamedAddr = Val; }
90 VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
91 bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; }
92 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
93 bool hasProtectedVisibility() const {
94 return Visibility == ProtectedVisibility;
96 void setVisibility(VisibilityTypes V) {
97 assert((!hasLocalLinkage() || V == DefaultVisibility) &&
98 "local linkage requires default visibility");
102 DLLStorageClassTypes getDLLStorageClass() const {
103 return DLLStorageClassTypes(DllStorageClass);
105 bool hasDLLImportStorageClass() const {
106 return DllStorageClass == DLLImportStorageClass;
108 bool hasDLLExportStorageClass() const {
109 return DllStorageClass == DLLExportStorageClass;
111 void setDLLStorageClass(DLLStorageClassTypes C) { DllStorageClass = C; }
113 bool hasSection() const { return !getSection().empty(); }
114 const std::string &getSection() const;
115 void setSection(StringRef S);
117 /// Global values are always pointers.
118 inline PointerType *getType() const {
119 return cast<PointerType>(User::getType());
122 static LinkageTypes getLinkOnceLinkage(bool ODR) {
123 return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;
125 static LinkageTypes getWeakLinkage(bool ODR) {
126 return ODR ? WeakODRLinkage : WeakAnyLinkage;
129 static bool isExternalLinkage(LinkageTypes Linkage) {
130 return Linkage == ExternalLinkage;
132 static bool isAvailableExternallyLinkage(LinkageTypes Linkage) {
133 return Linkage == AvailableExternallyLinkage;
135 static bool isLinkOnceLinkage(LinkageTypes Linkage) {
136 return Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage;
138 static bool isWeakLinkage(LinkageTypes Linkage) {
139 return Linkage == WeakAnyLinkage || Linkage == WeakODRLinkage;
141 static bool isAppendingLinkage(LinkageTypes Linkage) {
142 return Linkage == AppendingLinkage;
144 static bool isInternalLinkage(LinkageTypes Linkage) {
145 return Linkage == InternalLinkage;
147 static bool isPrivateLinkage(LinkageTypes Linkage) {
148 return Linkage == PrivateLinkage;
150 static bool isLocalLinkage(LinkageTypes Linkage) {
151 return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage);
153 static bool isExternalWeakLinkage(LinkageTypes Linkage) {
154 return Linkage == ExternalWeakLinkage;
156 static bool isCommonLinkage(LinkageTypes Linkage) {
157 return Linkage == CommonLinkage;
160 /// Whether the definition of this global may be discarded if it is not used
161 /// in its compilation unit.
162 static bool isDiscardableIfUnused(LinkageTypes Linkage) {
163 return isLinkOnceLinkage(Linkage) || isLocalLinkage(Linkage);
166 /// Whether the definition of this global may be replaced by something
167 /// non-equivalent at link time. For example, if a function has weak linkage
168 /// then the code defining it may be replaced by different code.
169 static bool mayBeOverridden(LinkageTypes Linkage) {
170 return Linkage == WeakAnyLinkage || Linkage == LinkOnceAnyLinkage ||
171 Linkage == CommonLinkage || Linkage == ExternalWeakLinkage;
174 /// Whether the definition of this global may be replaced at link time. NB:
175 /// Using this method outside of the code generators is almost always a
176 /// mistake: when working at the IR level use mayBeOverridden instead as it
177 /// knows about ODR semantics.
178 static bool isWeakForLinker(LinkageTypes Linkage) {
179 return Linkage == AvailableExternallyLinkage || Linkage == WeakAnyLinkage ||
180 Linkage == WeakODRLinkage || Linkage == LinkOnceAnyLinkage ||
181 Linkage == LinkOnceODRLinkage || Linkage == CommonLinkage ||
182 Linkage == ExternalWeakLinkage;
185 bool hasExternalLinkage() const { return isExternalLinkage(Linkage); }
186 bool hasAvailableExternallyLinkage() const {
187 return isAvailableExternallyLinkage(Linkage);
189 bool hasLinkOnceLinkage() const {
190 return isLinkOnceLinkage(Linkage);
192 bool hasWeakLinkage() const {
193 return isWeakLinkage(Linkage);
195 bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage); }
196 bool hasInternalLinkage() const { return isInternalLinkage(Linkage); }
197 bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); }
198 bool hasLocalLinkage() const { return isLocalLinkage(Linkage); }
199 bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); }
200 bool hasCommonLinkage() const { return isCommonLinkage(Linkage); }
202 void setLinkage(LinkageTypes LT) {
203 assert((!isLocalLinkage(LT) || hasDefaultVisibility()) &&
204 "local linkage requires default visibility");
207 LinkageTypes getLinkage() const { return Linkage; }
209 bool isDiscardableIfUnused() const {
210 return isDiscardableIfUnused(Linkage);
213 bool mayBeOverridden() const { return mayBeOverridden(Linkage); }
215 bool isWeakForLinker() const { return isWeakForLinker(Linkage); }
217 /// Copy all additional attributes (those not needed to create a GlobalValue)
218 /// from the GlobalValue Src to this one.
219 virtual void copyAttributesFrom(const GlobalValue *Src);
221 /// If special LLVM prefix that is used to inform the asm printer to not emit
222 /// usual symbol prefix before the symbol name is used then return linkage
223 /// name after skipping this special LLVM prefix.
224 static StringRef getRealLinkageName(StringRef Name) {
225 if (!Name.empty() && Name[0] == '\1')
226 return Name.substr(1);
230 /// @name Materialization
231 /// Materialization is used to construct functions only as they're needed. This
232 /// is useful to reduce memory usage in LLVM or parsing work done by the
233 /// BitcodeReader to load the Module.
236 /// If this function's Module is being lazily streamed in functions from disk
237 /// or some other source, this method can be used to check to see if the
238 /// function has been read in yet or not.
239 bool isMaterializable() const;
241 /// Returns true if this function was loaded from a GVMaterializer that's
242 /// still attached to its Module and that knows how to dematerialize the
244 bool isDematerializable() const;
246 /// Make sure this GlobalValue is fully read. If the module is corrupt, this
247 /// returns true and fills in the optional string with information about the
248 /// problem. If successful, this returns false.
249 bool Materialize(std::string *ErrInfo = nullptr);
251 /// If this GlobalValue is read in, and if the GVMaterializer supports it,
252 /// release the memory for the function, and set it up to be materialized
253 /// lazily. If !isDematerializable(), this method is a noop.
254 void Dematerialize();
258 /// Override from Constant class.
259 void destroyConstant() override;
261 /// Return true if the primary definition of this global value is outside of
262 /// the current translation unit.
263 bool isDeclaration() const;
265 /// This method unlinks 'this' from the containing module, but does not delete
267 virtual void removeFromParent() = 0;
269 /// This method unlinks 'this' from the containing module and deletes it.
270 virtual void eraseFromParent() = 0;
272 /// Get the module that this global value is contained inside of...
273 inline Module *getParent() { return Parent; }
274 inline const Module *getParent() const { return Parent; }
276 const DataLayout *getDataLayout() const;
278 // Methods for support type inquiry through isa, cast, and dyn_cast:
279 static inline bool classof(const Value *V) {
280 return V->getValueID() == Value::FunctionVal ||
281 V->getValueID() == Value::GlobalVariableVal ||
282 V->getValueID() == Value::GlobalAliasVal;
286 } // End llvm namespace