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"
23 #include <system_error>
35 class GlobalValue : public Constant {
36 GlobalValue(const GlobalValue &) = delete;
38 /// @brief An enumeration for the kinds of linkage for global values.
40 ExternalLinkage = 0,///< Externally visible function
41 AvailableExternallyLinkage, ///< Available for inspection, not emission.
42 LinkOnceAnyLinkage, ///< Keep one copy of function when linking (inline)
43 LinkOnceODRLinkage, ///< Same, but only replaced by something equivalent.
44 WeakAnyLinkage, ///< Keep one copy of named function when linking (weak)
45 WeakODRLinkage, ///< Same, but only replaced by something equivalent.
46 AppendingLinkage, ///< Special purpose, only applies to global arrays
47 InternalLinkage, ///< Rename collisions when linking (static functions).
48 PrivateLinkage, ///< Like Internal, but omit from symbol table.
49 ExternalWeakLinkage,///< ExternalWeak linkage description.
50 CommonLinkage ///< Tentative definitions.
53 /// @brief An enumeration for the kinds of visibility of global values.
54 enum VisibilityTypes {
55 DefaultVisibility = 0, ///< The GV is visible
56 HiddenVisibility, ///< The GV is hidden
57 ProtectedVisibility ///< The GV is protected
60 /// @brief Storage classes of global values for PE targets.
61 enum DLLStorageClassTypes {
62 DefaultStorageClass = 0,
63 DLLImportStorageClass = 1, ///< Function to be imported from DLL
64 DLLExportStorageClass = 2 ///< Function to be accessible from DLL.
68 GlobalValue(PointerType *Ty, ValueTy VTy, Use *Ops, unsigned NumOps,
69 LinkageTypes Linkage, const Twine &Name)
70 : Constant(Ty, VTy, Ops, NumOps), Linkage(Linkage),
71 Visibility(DefaultVisibility), UnnamedAddr(0),
72 DllStorageClass(DefaultStorageClass),
73 ThreadLocal(NotThreadLocal), IntID((Intrinsic::ID)0U), Parent(nullptr) {
77 // Note: VC++ treats enums as signed, so an extra bit is required to prevent
78 // Linkage and Visibility from turning into negative values.
79 LinkageTypes Linkage : 5; // The linkage of this global
80 unsigned Visibility : 2; // The visibility style of this global
81 unsigned UnnamedAddr : 1; // This value's address is not significant
82 unsigned DllStorageClass : 2; // DLL storage class
84 unsigned ThreadLocal : 3; // Is this symbol "Thread Local", if so, what is
86 static const unsigned GlobalValueSubClassDataBits = 19;
89 // Give subclasses access to what otherwise would be wasted padding.
90 // (19 + 3 + 2 + 1 + 2 + 5) == 32.
91 unsigned SubClassData : GlobalValueSubClassDataBits;
93 friend class Constant;
94 void destroyConstantImpl();
95 void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U) override;
98 /// \brief The intrinsic ID for this subclass (which must be a Function).
100 /// This member is defined by this class, but not used for anything.
101 /// Subclasses can use it to store their intrinsic ID, if they have one.
103 /// This is stored here to save space in Function on 64-bit hosts.
106 unsigned getGlobalValueSubClassData() const {
109 void setGlobalValueSubClassData(unsigned V) {
110 assert(V < (1 << GlobalValueSubClassDataBits) && "It will not fit");
114 Module *Parent; // The containing module.
116 enum ThreadLocalMode {
118 GeneralDynamicTLSModel,
119 LocalDynamicTLSModel,
124 ~GlobalValue() override {
125 removeDeadConstantUsers(); // remove any dead constants using this.
128 unsigned getAlignment() const;
130 bool hasUnnamedAddr() const { return UnnamedAddr; }
131 void setUnnamedAddr(bool Val) { UnnamedAddr = Val; }
133 bool hasComdat() const { return getComdat() != nullptr; }
135 const Comdat *getComdat() const {
136 return const_cast<GlobalValue *>(this)->getComdat();
139 VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
140 bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; }
141 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
142 bool hasProtectedVisibility() const {
143 return Visibility == ProtectedVisibility;
145 void setVisibility(VisibilityTypes V) {
146 assert((!hasLocalLinkage() || V == DefaultVisibility) &&
147 "local linkage requires default visibility");
151 /// If the value is "Thread Local", its value isn't shared by the threads.
152 bool isThreadLocal() const { return getThreadLocalMode() != NotThreadLocal; }
153 void setThreadLocal(bool Val) {
154 setThreadLocalMode(Val ? GeneralDynamicTLSModel : NotThreadLocal);
156 void setThreadLocalMode(ThreadLocalMode Val) {
157 assert(Val == NotThreadLocal || getValueID() != Value::FunctionVal);
160 ThreadLocalMode getThreadLocalMode() const {
161 return static_cast<ThreadLocalMode>(ThreadLocal);
164 DLLStorageClassTypes getDLLStorageClass() const {
165 return DLLStorageClassTypes(DllStorageClass);
167 bool hasDLLImportStorageClass() const {
168 return DllStorageClass == DLLImportStorageClass;
170 bool hasDLLExportStorageClass() const {
171 return DllStorageClass == DLLExportStorageClass;
173 void setDLLStorageClass(DLLStorageClassTypes C) { DllStorageClass = C; }
175 bool hasSection() const { return !StringRef(getSection()).empty(); }
176 // It is unfortunate that we have to use "char *" in here since this is
177 // always non NULL, but:
178 // * The C API expects a null terminated string, so we cannot use StringRef.
179 // * The C API expects us to own it, so we cannot use a std:string.
180 // * For GlobalAliases we can fail to find the section and we have to
181 // return "", so we cannot use a "const std::string &".
182 const char *getSection() const;
184 /// Global values are always pointers.
185 PointerType *getType() const { return cast<PointerType>(User::getType()); }
187 Type *getValueType() const { return getType()->getElementType(); }
189 static LinkageTypes getLinkOnceLinkage(bool ODR) {
190 return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;
192 static LinkageTypes getWeakLinkage(bool ODR) {
193 return ODR ? WeakODRLinkage : WeakAnyLinkage;
196 static bool isExternalLinkage(LinkageTypes Linkage) {
197 return Linkage == ExternalLinkage;
199 static bool isAvailableExternallyLinkage(LinkageTypes Linkage) {
200 return Linkage == AvailableExternallyLinkage;
202 static bool isLinkOnceODRLinkage(LinkageTypes Linkage) {
203 return Linkage == LinkOnceODRLinkage;
205 static bool isLinkOnceLinkage(LinkageTypes Linkage) {
206 return Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage;
208 static bool isWeakAnyLinkage(LinkageTypes Linkage) {
209 return Linkage == WeakAnyLinkage;
211 static bool isWeakODRLinkage(LinkageTypes Linkage) {
212 return Linkage == WeakODRLinkage;
214 static bool isWeakLinkage(LinkageTypes Linkage) {
215 return isWeakAnyLinkage(Linkage) || isWeakODRLinkage(Linkage);
217 static bool isAppendingLinkage(LinkageTypes Linkage) {
218 return Linkage == AppendingLinkage;
220 static bool isInternalLinkage(LinkageTypes Linkage) {
221 return Linkage == InternalLinkage;
223 static bool isPrivateLinkage(LinkageTypes Linkage) {
224 return Linkage == PrivateLinkage;
226 static bool isLocalLinkage(LinkageTypes Linkage) {
227 return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage);
229 static bool isExternalWeakLinkage(LinkageTypes Linkage) {
230 return Linkage == ExternalWeakLinkage;
232 static bool isCommonLinkage(LinkageTypes Linkage) {
233 return Linkage == CommonLinkage;
236 /// Whether the definition of this global may be discarded if it is not used
237 /// in its compilation unit.
238 static bool isDiscardableIfUnused(LinkageTypes Linkage) {
239 return isLinkOnceLinkage(Linkage) || isLocalLinkage(Linkage);
242 /// Whether the definition of this global may be replaced by something
243 /// non-equivalent at link time. For example, if a function has weak linkage
244 /// then the code defining it may be replaced by different code.
245 static bool mayBeOverridden(LinkageTypes Linkage) {
246 return Linkage == WeakAnyLinkage || Linkage == LinkOnceAnyLinkage ||
247 Linkage == CommonLinkage || Linkage == ExternalWeakLinkage;
250 /// Whether the definition of this global may be replaced at link time. NB:
251 /// Using this method outside of the code generators is almost always a
252 /// mistake: when working at the IR level use mayBeOverridden instead as it
253 /// knows about ODR semantics.
254 static bool isWeakForLinker(LinkageTypes Linkage) {
255 return Linkage == AvailableExternallyLinkage || Linkage == WeakAnyLinkage ||
256 Linkage == WeakODRLinkage || Linkage == LinkOnceAnyLinkage ||
257 Linkage == LinkOnceODRLinkage || Linkage == CommonLinkage ||
258 Linkage == ExternalWeakLinkage;
261 bool hasExternalLinkage() const { return isExternalLinkage(Linkage); }
262 bool hasAvailableExternallyLinkage() const {
263 return isAvailableExternallyLinkage(Linkage);
265 bool hasLinkOnceLinkage() const {
266 return isLinkOnceLinkage(Linkage);
268 bool hasLinkOnceODRLinkage() const { return isLinkOnceODRLinkage(Linkage); }
269 bool hasWeakLinkage() const {
270 return isWeakLinkage(Linkage);
272 bool hasWeakAnyLinkage() const {
273 return isWeakAnyLinkage(Linkage);
275 bool hasWeakODRLinkage() const {
276 return isWeakODRLinkage(Linkage);
278 bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage); }
279 bool hasInternalLinkage() const { return isInternalLinkage(Linkage); }
280 bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); }
281 bool hasLocalLinkage() const { return isLocalLinkage(Linkage); }
282 bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); }
283 bool hasCommonLinkage() const { return isCommonLinkage(Linkage); }
285 void setLinkage(LinkageTypes LT) {
286 if (isLocalLinkage(LT))
287 Visibility = DefaultVisibility;
290 LinkageTypes getLinkage() const { return Linkage; }
292 bool isDiscardableIfUnused() const {
293 return isDiscardableIfUnused(Linkage);
296 bool mayBeOverridden() const { return mayBeOverridden(Linkage); }
298 bool isWeakForLinker() const { return isWeakForLinker(Linkage); }
300 /// Copy all additional attributes (those not needed to create a GlobalValue)
301 /// from the GlobalValue Src to this one.
302 virtual void copyAttributesFrom(const GlobalValue *Src);
304 /// If special LLVM prefix that is used to inform the asm printer to not emit
305 /// usual symbol prefix before the symbol name is used then return linkage
306 /// name after skipping this special LLVM prefix.
307 static StringRef getRealLinkageName(StringRef Name) {
308 if (!Name.empty() && Name[0] == '\1')
309 return Name.substr(1);
313 /// @name Materialization
314 /// Materialization is used to construct functions only as they're needed. This
315 /// is useful to reduce memory usage in LLVM or parsing work done by the
316 /// BitcodeReader to load the Module.
319 /// If this function's Module is being lazily streamed in functions from disk
320 /// or some other source, this method can be used to check to see if the
321 /// function has been read in yet or not.
322 bool isMaterializable() const;
324 /// Returns true if this function was loaded from a GVMaterializer that's
325 /// still attached to its Module and that knows how to dematerialize the
327 bool isDematerializable() const;
329 /// Make sure this GlobalValue is fully read. If the module is corrupt, this
330 /// returns true and fills in the optional string with information about the
331 /// problem. If successful, this returns false.
332 std::error_code materialize();
334 /// If this GlobalValue is read in, and if the GVMaterializer supports it,
335 /// release the memory for the function, and set it up to be materialized
336 /// lazily. If !isDematerializable(), this method is a noop.
337 void dematerialize();
341 /// Return true if the primary definition of this global value is outside of
342 /// the current translation unit.
343 bool isDeclaration() const;
345 bool isDeclarationForLinker() const {
346 if (hasAvailableExternallyLinkage())
349 return isDeclaration();
352 /// This method unlinks 'this' from the containing module, but does not delete
354 virtual void removeFromParent() = 0;
356 /// This method unlinks 'this' from the containing module and deletes it.
357 virtual void eraseFromParent() = 0;
359 /// Get the module that this global value is contained inside of...
360 Module *getParent() { return Parent; }
361 const Module *getParent() const { return Parent; }
363 // Methods for support type inquiry through isa, cast, and dyn_cast:
364 static bool classof(const Value *V) {
365 return V->getValueID() == Value::FunctionVal ||
366 V->getValueID() == Value::GlobalVariableVal ||
367 V->getValueID() == Value::GlobalAliasVal;
371 } // End llvm namespace