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),
67 ThreadLocal(NotThreadLocal), Parent(nullptr) {
71 // Note: VC++ treats enums as signed, so an extra bit is required to prevent
72 // Linkage and Visibility from turning into negative values.
73 LinkageTypes Linkage : 5; // The linkage of this global
74 unsigned Visibility : 2; // The visibility style of this global
75 unsigned UnnamedAddr : 1; // This value's address is not significant
76 unsigned DllStorageClass : 2; // DLL storage class
78 unsigned ThreadLocal : 3; // Is this symbol "Thread Local", if so, what is
82 // Give subclasses access to what otherwise would be wasted padding.
83 // (19 + 3 + 2 + 1 + 2 + 5) == 32.
84 unsigned SubClassData : 19;
86 unsigned getGlobalValueSubClassData() const {
89 void setGlobalValueSubClassData(unsigned V) {
90 assert(V < (1 << 19) && "It will not fit");
94 Module *Parent; // The containing module.
96 enum ThreadLocalMode {
98 GeneralDynamicTLSModel,
105 removeDeadConstantUsers(); // remove any dead constants using this.
108 unsigned getAlignment() const;
110 bool hasUnnamedAddr() const { return UnnamedAddr; }
111 void setUnnamedAddr(bool Val) { UnnamedAddr = Val; }
113 VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
114 bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; }
115 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
116 bool hasProtectedVisibility() const {
117 return Visibility == ProtectedVisibility;
119 void setVisibility(VisibilityTypes V) {
120 assert((!hasLocalLinkage() || V == DefaultVisibility) &&
121 "local linkage requires default visibility");
125 /// If the value is "Thread Local", its value isn't shared by the threads.
126 bool isThreadLocal() const { return getThreadLocalMode() != NotThreadLocal; }
127 void setThreadLocal(bool Val) {
128 setThreadLocalMode(Val ? GeneralDynamicTLSModel : NotThreadLocal);
130 void setThreadLocalMode(ThreadLocalMode Val) {
131 assert(Val == NotThreadLocal || getValueID() != Value::FunctionVal);
134 ThreadLocalMode getThreadLocalMode() const {
135 return static_cast<ThreadLocalMode>(ThreadLocal);
138 DLLStorageClassTypes getDLLStorageClass() const {
139 return DLLStorageClassTypes(DllStorageClass);
141 bool hasDLLImportStorageClass() const {
142 return DllStorageClass == DLLImportStorageClass;
144 bool hasDLLExportStorageClass() const {
145 return DllStorageClass == DLLExportStorageClass;
147 void setDLLStorageClass(DLLStorageClassTypes C) { DllStorageClass = C; }
149 bool hasSection() const { return !StringRef(getSection()).empty(); }
150 // It is unfortunate that we have to use "char *" in here since this is
151 // always non NULL, but:
152 // * The C API expects a null terminated string, so we cannot use StringRef.
153 // * The C API expects us to own it, so we cannot use a std:string.
154 // * For GlobalAliases we can fail to find the section and we have to
155 // return "", so we cannot use a "const std::string &".
156 const char *getSection() const;
158 /// Global values are always pointers.
159 inline PointerType *getType() const {
160 return cast<PointerType>(User::getType());
163 static LinkageTypes getLinkOnceLinkage(bool ODR) {
164 return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;
166 static LinkageTypes getWeakLinkage(bool ODR) {
167 return ODR ? WeakODRLinkage : WeakAnyLinkage;
170 static bool isExternalLinkage(LinkageTypes Linkage) {
171 return Linkage == ExternalLinkage;
173 static bool isAvailableExternallyLinkage(LinkageTypes Linkage) {
174 return Linkage == AvailableExternallyLinkage;
176 static bool isLinkOnceLinkage(LinkageTypes Linkage) {
177 return Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage;
179 static bool isWeakAnyLinkage(LinkageTypes Linkage) {
180 return Linkage == WeakAnyLinkage;
182 static bool isWeakODRLinkage(LinkageTypes Linkage) {
183 return Linkage == WeakODRLinkage;
185 static bool isWeakLinkage(LinkageTypes Linkage) {
186 return isWeakAnyLinkage(Linkage) || isWeakODRLinkage(Linkage);
188 static bool isAppendingLinkage(LinkageTypes Linkage) {
189 return Linkage == AppendingLinkage;
191 static bool isInternalLinkage(LinkageTypes Linkage) {
192 return Linkage == InternalLinkage;
194 static bool isPrivateLinkage(LinkageTypes Linkage) {
195 return Linkage == PrivateLinkage;
197 static bool isLocalLinkage(LinkageTypes Linkage) {
198 return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage);
200 static bool isExternalWeakLinkage(LinkageTypes Linkage) {
201 return Linkage == ExternalWeakLinkage;
203 static bool isCommonLinkage(LinkageTypes Linkage) {
204 return Linkage == CommonLinkage;
207 /// Whether the definition of this global may be discarded if it is not used
208 /// in its compilation unit.
209 static bool isDiscardableIfUnused(LinkageTypes Linkage) {
210 return isLinkOnceLinkage(Linkage) || isLocalLinkage(Linkage);
213 /// Whether the definition of this global may be replaced by something
214 /// non-equivalent at link time. For example, if a function has weak linkage
215 /// then the code defining it may be replaced by different code.
216 static bool mayBeOverridden(LinkageTypes Linkage) {
217 return Linkage == WeakAnyLinkage || Linkage == LinkOnceAnyLinkage ||
218 Linkage == CommonLinkage || Linkage == ExternalWeakLinkage;
221 /// Whether the definition of this global may be replaced at link time. NB:
222 /// Using this method outside of the code generators is almost always a
223 /// mistake: when working at the IR level use mayBeOverridden instead as it
224 /// knows about ODR semantics.
225 static bool isWeakForLinker(LinkageTypes Linkage) {
226 return Linkage == AvailableExternallyLinkage || Linkage == WeakAnyLinkage ||
227 Linkage == WeakODRLinkage || Linkage == LinkOnceAnyLinkage ||
228 Linkage == LinkOnceODRLinkage || Linkage == CommonLinkage ||
229 Linkage == ExternalWeakLinkage;
232 bool hasExternalLinkage() const { return isExternalLinkage(Linkage); }
233 bool hasAvailableExternallyLinkage() const {
234 return isAvailableExternallyLinkage(Linkage);
236 bool hasLinkOnceLinkage() const {
237 return isLinkOnceLinkage(Linkage);
239 bool hasWeakLinkage() const {
240 return isWeakLinkage(Linkage);
242 bool hasWeakAnyLinkage() const {
243 return isWeakAnyLinkage(Linkage);
245 bool hasWeakODRLinkage() const {
246 return isWeakODRLinkage(Linkage);
248 bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage); }
249 bool hasInternalLinkage() const { return isInternalLinkage(Linkage); }
250 bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); }
251 bool hasLocalLinkage() const { return isLocalLinkage(Linkage); }
252 bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); }
253 bool hasCommonLinkage() const { return isCommonLinkage(Linkage); }
255 void setLinkage(LinkageTypes LT) {
256 if (isLocalLinkage(LT))
257 Visibility = DefaultVisibility;
260 LinkageTypes getLinkage() const { return Linkage; }
262 bool isDiscardableIfUnused() const {
263 return isDiscardableIfUnused(Linkage);
266 bool mayBeOverridden() const { return mayBeOverridden(Linkage); }
268 bool isWeakForLinker() const { return isWeakForLinker(Linkage); }
270 /// Copy all additional attributes (those not needed to create a GlobalValue)
271 /// from the GlobalValue Src to this one.
272 virtual void copyAttributesFrom(const GlobalValue *Src);
274 /// If special LLVM prefix that is used to inform the asm printer to not emit
275 /// usual symbol prefix before the symbol name is used then return linkage
276 /// name after skipping this special LLVM prefix.
277 static StringRef getRealLinkageName(StringRef Name) {
278 if (!Name.empty() && Name[0] == '\1')
279 return Name.substr(1);
283 /// @name Materialization
284 /// Materialization is used to construct functions only as they're needed. This
285 /// is useful to reduce memory usage in LLVM or parsing work done by the
286 /// BitcodeReader to load the Module.
289 /// If this function's Module is being lazily streamed in functions from disk
290 /// or some other source, this method can be used to check to see if the
291 /// function has been read in yet or not.
292 bool isMaterializable() const;
294 /// Returns true if this function was loaded from a GVMaterializer that's
295 /// still attached to its Module and that knows how to dematerialize the
297 bool isDematerializable() const;
299 /// Make sure this GlobalValue is fully read. If the module is corrupt, this
300 /// returns true and fills in the optional string with information about the
301 /// problem. If successful, this returns false.
302 bool Materialize(std::string *ErrInfo = nullptr);
304 /// If this GlobalValue is read in, and if the GVMaterializer supports it,
305 /// release the memory for the function, and set it up to be materialized
306 /// lazily. If !isDematerializable(), this method is a noop.
307 void Dematerialize();
311 /// Override from Constant class.
312 void destroyConstant() override;
314 /// Return true if the primary definition of this global value is outside of
315 /// the current translation unit.
316 bool isDeclaration() const;
318 /// This method unlinks 'this' from the containing module, but does not delete
320 virtual void removeFromParent() = 0;
322 /// This method unlinks 'this' from the containing module and deletes it.
323 virtual void eraseFromParent() = 0;
325 /// Get the module that this global value is contained inside of...
326 inline Module *getParent() { return Parent; }
327 inline const Module *getParent() const { return Parent; }
329 const DataLayout *getDataLayout() const;
331 // Methods for support type inquiry through isa, cast, and dyn_cast:
332 static inline bool classof(const Value *V) {
333 return V->getValueID() == Value::FunctionVal ||
334 V->getValueID() == Value::GlobalVariableVal ||
335 V->getValueID() == Value::GlobalAliasVal;
339 } // End llvm namespace