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"
30 class GlobalValue : public Constant {
31 GlobalValue(const GlobalValue &) LLVM_DELETED_FUNCTION;
33 /// @brief An enumeration for the kinds of linkage for global values.
35 ExternalLinkage = 0,///< Externally visible function
36 AvailableExternallyLinkage, ///< Available for inspection, not emission.
37 LinkOnceAnyLinkage, ///< Keep one copy of function when linking (inline)
38 LinkOnceODRLinkage, ///< Same, but only replaced by something equivalent.
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 ExternalWeakLinkage,///< ExternalWeak linkage description.
45 CommonLinkage ///< Tentative definitions.
48 /// @brief An enumeration for the kinds of visibility of global values.
49 enum VisibilityTypes {
50 DefaultVisibility = 0, ///< The GV is visible
51 HiddenVisibility, ///< The GV is hidden
52 ProtectedVisibility ///< The GV is protected
55 /// @brief Storage classes of global values for PE targets.
56 enum DLLStorageClassTypes {
57 DefaultStorageClass = 0,
58 DLLImportStorageClass = 1, ///< Function to be imported from DLL
59 DLLExportStorageClass = 2 ///< Function to be accessible from DLL.
63 GlobalValue(Type *Ty, ValueTy VTy, Use *Ops, unsigned NumOps,
64 LinkageTypes Linkage, const Twine &Name)
65 : Constant(Ty, VTy, Ops, NumOps), Linkage(Linkage),
66 Visibility(DefaultVisibility), UnnamedAddr(0),
67 DllStorageClass(DefaultStorageClass),
68 ThreadLocal(NotThreadLocal), Parent(nullptr) {
72 // Note: VC++ treats enums as signed, so an extra bit is required to prevent
73 // Linkage and Visibility from turning into negative values.
74 LinkageTypes Linkage : 5; // The linkage of this global
75 unsigned Visibility : 2; // The visibility style of this global
76 unsigned UnnamedAddr : 1; // This value's address is not significant
77 unsigned DllStorageClass : 2; // DLL storage class
79 unsigned ThreadLocal : 3; // Is this symbol "Thread Local", if so, what is
83 // Give subclasses access to what otherwise would be wasted padding.
84 // (19 + 3 + 2 + 1 + 2 + 5) == 32.
85 unsigned SubClassData : 19;
87 unsigned getGlobalValueSubClassData() const {
90 void setGlobalValueSubClassData(unsigned V) {
91 assert(V < (1 << 19) && "It will not fit");
95 Module *Parent; // The containing module.
97 enum ThreadLocalMode {
99 GeneralDynamicTLSModel,
100 LocalDynamicTLSModel,
106 removeDeadConstantUsers(); // remove any dead constants using this.
109 unsigned getAlignment() const;
111 bool hasUnnamedAddr() const { return UnnamedAddr; }
112 void setUnnamedAddr(bool Val) { UnnamedAddr = Val; }
114 bool hasComdat() const { return getComdat() != nullptr; }
116 const Comdat *getComdat() const {
117 return const_cast<GlobalValue *>(this)->getComdat();
120 VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
121 bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; }
122 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
123 bool hasProtectedVisibility() const {
124 return Visibility == ProtectedVisibility;
126 void setVisibility(VisibilityTypes V) {
127 assert((!hasLocalLinkage() || V == DefaultVisibility) &&
128 "local linkage requires default visibility");
132 /// If the value is "Thread Local", its value isn't shared by the threads.
133 bool isThreadLocal() const { return getThreadLocalMode() != NotThreadLocal; }
134 void setThreadLocal(bool Val) {
135 setThreadLocalMode(Val ? GeneralDynamicTLSModel : NotThreadLocal);
137 void setThreadLocalMode(ThreadLocalMode Val) {
138 assert(Val == NotThreadLocal || getValueID() != Value::FunctionVal);
141 ThreadLocalMode getThreadLocalMode() const {
142 return static_cast<ThreadLocalMode>(ThreadLocal);
145 DLLStorageClassTypes getDLLStorageClass() const {
146 return DLLStorageClassTypes(DllStorageClass);
148 bool hasDLLImportStorageClass() const {
149 return DllStorageClass == DLLImportStorageClass;
151 bool hasDLLExportStorageClass() const {
152 return DllStorageClass == DLLExportStorageClass;
154 void setDLLStorageClass(DLLStorageClassTypes C) { DllStorageClass = C; }
156 bool hasSection() const { return !StringRef(getSection()).empty(); }
157 // It is unfortunate that we have to use "char *" in here since this is
158 // always non NULL, but:
159 // * The C API expects a null terminated string, so we cannot use StringRef.
160 // * The C API expects us to own it, so we cannot use a std:string.
161 // * For GlobalAliases we can fail to find the section and we have to
162 // return "", so we cannot use a "const std::string &".
163 const char *getSection() const;
165 /// Global values are always pointers.
166 inline PointerType *getType() const {
167 return cast<PointerType>(User::getType());
170 static LinkageTypes getLinkOnceLinkage(bool ODR) {
171 return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;
173 static LinkageTypes getWeakLinkage(bool ODR) {
174 return ODR ? WeakODRLinkage : WeakAnyLinkage;
177 static bool isExternalLinkage(LinkageTypes Linkage) {
178 return Linkage == ExternalLinkage;
180 static bool isAvailableExternallyLinkage(LinkageTypes Linkage) {
181 return Linkage == AvailableExternallyLinkage;
183 static bool isLinkOnceODRLinkage(LinkageTypes Linkage) {
184 return Linkage == LinkOnceODRLinkage;
186 static bool isLinkOnceLinkage(LinkageTypes Linkage) {
187 return Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage;
189 static bool isWeakAnyLinkage(LinkageTypes Linkage) {
190 return Linkage == WeakAnyLinkage;
192 static bool isWeakODRLinkage(LinkageTypes Linkage) {
193 return Linkage == WeakODRLinkage;
195 static bool isWeakLinkage(LinkageTypes Linkage) {
196 return isWeakAnyLinkage(Linkage) || isWeakODRLinkage(Linkage);
198 static bool isAppendingLinkage(LinkageTypes Linkage) {
199 return Linkage == AppendingLinkage;
201 static bool isInternalLinkage(LinkageTypes Linkage) {
202 return Linkage == InternalLinkage;
204 static bool isPrivateLinkage(LinkageTypes Linkage) {
205 return Linkage == PrivateLinkage;
207 static bool isLocalLinkage(LinkageTypes Linkage) {
208 return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage);
210 static bool isExternalWeakLinkage(LinkageTypes Linkage) {
211 return Linkage == ExternalWeakLinkage;
213 static bool isCommonLinkage(LinkageTypes Linkage) {
214 return Linkage == CommonLinkage;
217 /// Whether the definition of this global may be discarded if it is not used
218 /// in its compilation unit.
219 static bool isDiscardableIfUnused(LinkageTypes Linkage) {
220 return isLinkOnceLinkage(Linkage) || isLocalLinkage(Linkage);
223 /// Whether the definition of this global may be replaced by something
224 /// non-equivalent at link time. For example, if a function has weak linkage
225 /// then the code defining it may be replaced by different code.
226 static bool mayBeOverridden(LinkageTypes Linkage) {
227 return Linkage == WeakAnyLinkage || Linkage == LinkOnceAnyLinkage ||
228 Linkage == CommonLinkage || Linkage == ExternalWeakLinkage;
231 /// Whether the definition of this global may be replaced at link time. NB:
232 /// Using this method outside of the code generators is almost always a
233 /// mistake: when working at the IR level use mayBeOverridden instead as it
234 /// knows about ODR semantics.
235 static bool isWeakForLinker(LinkageTypes Linkage) {
236 return Linkage == AvailableExternallyLinkage || Linkage == WeakAnyLinkage ||
237 Linkage == WeakODRLinkage || Linkage == LinkOnceAnyLinkage ||
238 Linkage == LinkOnceODRLinkage || Linkage == CommonLinkage ||
239 Linkage == ExternalWeakLinkage;
242 bool hasExternalLinkage() const { return isExternalLinkage(Linkage); }
243 bool hasAvailableExternallyLinkage() const {
244 return isAvailableExternallyLinkage(Linkage);
246 bool hasLinkOnceLinkage() const {
247 return isLinkOnceLinkage(Linkage);
249 bool hasLinkOnceODRLinkage() const { return isLinkOnceODRLinkage(Linkage); }
250 bool hasWeakLinkage() const {
251 return isWeakLinkage(Linkage);
253 bool hasWeakAnyLinkage() const {
254 return isWeakAnyLinkage(Linkage);
256 bool hasWeakODRLinkage() const {
257 return isWeakODRLinkage(Linkage);
259 bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage); }
260 bool hasInternalLinkage() const { return isInternalLinkage(Linkage); }
261 bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); }
262 bool hasLocalLinkage() const { return isLocalLinkage(Linkage); }
263 bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); }
264 bool hasCommonLinkage() const { return isCommonLinkage(Linkage); }
266 void setLinkage(LinkageTypes LT) {
267 if (isLocalLinkage(LT))
268 Visibility = DefaultVisibility;
271 LinkageTypes getLinkage() const { return Linkage; }
273 bool isDiscardableIfUnused() const {
274 return isDiscardableIfUnused(Linkage);
277 bool mayBeOverridden() const { return mayBeOverridden(Linkage); }
279 bool isWeakForLinker() const { return isWeakForLinker(Linkage); }
281 /// Copy all additional attributes (those not needed to create a GlobalValue)
282 /// from the GlobalValue Src to this one.
283 virtual void copyAttributesFrom(const GlobalValue *Src);
285 /// If special LLVM prefix that is used to inform the asm printer to not emit
286 /// usual symbol prefix before the symbol name is used then return linkage
287 /// name after skipping this special LLVM prefix.
288 static StringRef getRealLinkageName(StringRef Name) {
289 if (!Name.empty() && Name[0] == '\1')
290 return Name.substr(1);
294 /// @name Materialization
295 /// Materialization is used to construct functions only as they're needed. This
296 /// is useful to reduce memory usage in LLVM or parsing work done by the
297 /// BitcodeReader to load the Module.
300 /// If this function's Module is being lazily streamed in functions from disk
301 /// or some other source, this method can be used to check to see if the
302 /// function has been read in yet or not.
303 bool isMaterializable() const;
305 /// Returns true if this function was loaded from a GVMaterializer that's
306 /// still attached to its Module and that knows how to dematerialize the
308 bool isDematerializable() const;
310 /// Make sure this GlobalValue is fully read. If the module is corrupt, this
311 /// returns true and fills in the optional string with information about the
312 /// problem. If successful, this returns false.
313 bool Materialize(std::string *ErrInfo = nullptr);
315 /// If this GlobalValue is read in, and if the GVMaterializer supports it,
316 /// release the memory for the function, and set it up to be materialized
317 /// lazily. If !isDematerializable(), this method is a noop.
318 void Dematerialize();
322 /// Override from Constant class.
323 void destroyConstant() override;
325 /// Return true if the primary definition of this global value is outside of
326 /// the current translation unit.
327 bool isDeclaration() const;
329 /// This method unlinks 'this' from the containing module, but does not delete
331 virtual void removeFromParent() = 0;
333 /// This method unlinks 'this' from the containing module and deletes it.
334 virtual void eraseFromParent() = 0;
336 /// Get the module that this global value is contained inside of...
337 inline Module *getParent() { return Parent; }
338 inline const Module *getParent() const { return Parent; }
340 const DataLayout *getDataLayout() const;
342 // Methods for support type inquiry through isa, cast, and dyn_cast:
343 static inline bool classof(const Value *V) {
344 return V->getValueID() == Value::FunctionVal ||
345 V->getValueID() == Value::GlobalVariableVal ||
346 V->getValueID() == Value::GlobalAliasVal;
350 } // End llvm namespace