• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 //===-- llvm/GlobalValue.h - Class to represent a global value --*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
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
14 // constant.
15 //
16 //===----------------------------------------------------------------------===//
17 
18 #ifndef LLVM_GLOBALVALUE_H
19 #define LLVM_GLOBALVALUE_H
20 
21 #include "llvm/Constant.h"
22 
23 namespace llvm {
24 
25 class PointerType;
26 class Module;
27 
28 class GlobalValue : public Constant {
29   GlobalValue(const GlobalValue &);             // do not implement
30 public:
31   /// @brief An enumeration for the kinds of linkage for global values.
32   enum LinkageTypes {
33     ExternalLinkage = 0,///< Externally visible function
34     AvailableExternallyLinkage, ///< Available for inspection, not emission.
35     LinkOnceAnyLinkage, ///< Keep one copy of function when linking (inline)
36     LinkOnceODRLinkage, ///< Same, but only replaced by something equivalent.
37     WeakAnyLinkage,     ///< Keep one copy of named function when linking (weak)
38     WeakODRLinkage,     ///< Same, but only replaced by something equivalent.
39     AppendingLinkage,   ///< Special purpose, only applies to global arrays
40     InternalLinkage,    ///< Rename collisions when linking (static functions).
41     PrivateLinkage,     ///< Like Internal, but omit from symbol table.
42     LinkerPrivateLinkage, ///< Like Private, but linker removes.
43     LinkerPrivateWeakLinkage, ///< Like LinkerPrivate, but weak.
44     LinkerPrivateWeakDefAutoLinkage, ///< Like LinkerPrivateWeak, but possibly
45                                      ///  hidden.
46     DLLImportLinkage,   ///< Function to be imported from DLL
47     DLLExportLinkage,   ///< Function to be accessible from DLL.
48     ExternalWeakLinkage,///< ExternalWeak linkage description.
49     CommonLinkage       ///< Tentative definitions.
50   };
51 
52   /// @brief An enumeration for the kinds of visibility of global values.
53   enum VisibilityTypes {
54     DefaultVisibility = 0,  ///< The GV is visible
55     HiddenVisibility,       ///< The GV is hidden
56     ProtectedVisibility     ///< The GV is protected
57   };
58 
59 protected:
GlobalValue(Type * ty,ValueTy vty,Use * Ops,unsigned NumOps,LinkageTypes linkage,const Twine & Name)60   GlobalValue(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps,
61               LinkageTypes linkage, const Twine &Name)
62     : Constant(ty, vty, Ops, NumOps), Parent(0),
63       Linkage(linkage), Visibility(DefaultVisibility), Alignment(0),
64       UnnamedAddr(0) {
65     setName(Name);
66   }
67 
68   Module *Parent;
69   // Note: VC++ treats enums as signed, so an extra bit is required to prevent
70   // Linkage and Visibility from turning into negative values.
71   LinkageTypes Linkage : 5;   // The linkage of this global
72   unsigned Visibility : 2;    // The visibility style of this global
73   unsigned Alignment : 16;    // Alignment of this symbol, must be power of two
74   unsigned UnnamedAddr : 1;   // This value's address is not significant
75   std::string Section;        // Section to emit this into, empty mean default
76 public:
~GlobalValue()77   ~GlobalValue() {
78     removeDeadConstantUsers();   // remove any dead constants using this.
79   }
80 
getAlignment()81   unsigned getAlignment() const {
82     return (1u << Alignment) >> 1;
83   }
84   void setAlignment(unsigned Align);
85 
hasUnnamedAddr()86   bool hasUnnamedAddr() const { return UnnamedAddr; }
setUnnamedAddr(bool Val)87   void setUnnamedAddr(bool Val) { UnnamedAddr = Val; }
88 
getVisibility()89   VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
hasDefaultVisibility()90   bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; }
hasHiddenVisibility()91   bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
hasProtectedVisibility()92   bool hasProtectedVisibility() const {
93     return Visibility == ProtectedVisibility;
94   }
setVisibility(VisibilityTypes V)95   void setVisibility(VisibilityTypes V) { Visibility = V; }
96 
hasSection()97   bool hasSection() const { return !Section.empty(); }
getSection()98   const std::string &getSection() const { return Section; }
setSection(StringRef S)99   void setSection(StringRef S) { Section = S; }
100 
101   /// If the usage is empty (except transitively dead constants), then this
102   /// global value can be safely deleted since the destructor will
103   /// delete the dead constants as well.
104   /// @brief Determine if the usage of this global value is empty except
105   /// for transitively dead constants.
106   bool use_empty_except_constants();
107 
108   /// getType - Global values are always pointers.
getType()109   inline PointerType *getType() const {
110     return reinterpret_cast<PointerType*>(User::getType());
111   }
112 
getLinkOnceLinkage(bool ODR)113   static LinkageTypes getLinkOnceLinkage(bool ODR) {
114     return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;
115   }
getWeakLinkage(bool ODR)116   static LinkageTypes getWeakLinkage(bool ODR) {
117     return ODR ? WeakODRLinkage : WeakAnyLinkage;
118   }
119 
isExternalLinkage(LinkageTypes Linkage)120   static bool isExternalLinkage(LinkageTypes Linkage) {
121     return Linkage == ExternalLinkage;
122   }
isAvailableExternallyLinkage(LinkageTypes Linkage)123   static bool isAvailableExternallyLinkage(LinkageTypes Linkage) {
124     return Linkage == AvailableExternallyLinkage;
125   }
isLinkOnceLinkage(LinkageTypes Linkage)126   static bool isLinkOnceLinkage(LinkageTypes Linkage) {
127     return Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage;
128   }
isWeakLinkage(LinkageTypes Linkage)129   static bool isWeakLinkage(LinkageTypes Linkage) {
130     return Linkage == WeakAnyLinkage || Linkage == WeakODRLinkage;
131   }
isAppendingLinkage(LinkageTypes Linkage)132   static bool isAppendingLinkage(LinkageTypes Linkage) {
133     return Linkage == AppendingLinkage;
134   }
isInternalLinkage(LinkageTypes Linkage)135   static bool isInternalLinkage(LinkageTypes Linkage) {
136     return Linkage == InternalLinkage;
137   }
isPrivateLinkage(LinkageTypes Linkage)138   static bool isPrivateLinkage(LinkageTypes Linkage) {
139     return Linkage == PrivateLinkage;
140   }
isLinkerPrivateLinkage(LinkageTypes Linkage)141   static bool isLinkerPrivateLinkage(LinkageTypes Linkage) {
142     return Linkage == LinkerPrivateLinkage;
143   }
isLinkerPrivateWeakLinkage(LinkageTypes Linkage)144   static bool isLinkerPrivateWeakLinkage(LinkageTypes Linkage) {
145     return Linkage == LinkerPrivateWeakLinkage;
146   }
isLinkerPrivateWeakDefAutoLinkage(LinkageTypes Linkage)147   static bool isLinkerPrivateWeakDefAutoLinkage(LinkageTypes Linkage) {
148     return Linkage == LinkerPrivateWeakDefAutoLinkage;
149   }
isLocalLinkage(LinkageTypes Linkage)150   static bool isLocalLinkage(LinkageTypes Linkage) {
151     return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage) ||
152       isLinkerPrivateLinkage(Linkage) || isLinkerPrivateWeakLinkage(Linkage) ||
153       isLinkerPrivateWeakDefAutoLinkage(Linkage);
154   }
isDLLImportLinkage(LinkageTypes Linkage)155   static bool isDLLImportLinkage(LinkageTypes Linkage) {
156     return Linkage == DLLImportLinkage;
157   }
isDLLExportLinkage(LinkageTypes Linkage)158   static bool isDLLExportLinkage(LinkageTypes Linkage) {
159     return Linkage == DLLExportLinkage;
160   }
isExternalWeakLinkage(LinkageTypes Linkage)161   static bool isExternalWeakLinkage(LinkageTypes Linkage) {
162     return Linkage == ExternalWeakLinkage;
163   }
isCommonLinkage(LinkageTypes Linkage)164   static bool isCommonLinkage(LinkageTypes Linkage) {
165     return Linkage == CommonLinkage;
166   }
167 
168   /// mayBeOverridden - Whether the definition of this global may be replaced
169   /// by something non-equivalent at link time.  For example, if a function has
170   /// weak linkage then the code defining it may be replaced by different code.
mayBeOverridden(LinkageTypes Linkage)171   static bool mayBeOverridden(LinkageTypes Linkage) {
172     return Linkage == WeakAnyLinkage ||
173            Linkage == LinkOnceAnyLinkage ||
174            Linkage == CommonLinkage ||
175            Linkage == ExternalWeakLinkage ||
176            Linkage == LinkerPrivateWeakLinkage ||
177            Linkage == LinkerPrivateWeakDefAutoLinkage;
178   }
179 
180   /// isWeakForLinker - Whether the definition of this global may be replaced at
181   /// link time.  NB: Using this method outside of the code generators is almost
182   /// always a mistake: when working at the IR level use mayBeOverridden instead
183   /// as it knows about ODR semantics.
isWeakForLinker(LinkageTypes Linkage)184   static bool isWeakForLinker(LinkageTypes Linkage)  {
185     return Linkage == AvailableExternallyLinkage ||
186            Linkage == WeakAnyLinkage ||
187            Linkage == WeakODRLinkage ||
188            Linkage == LinkOnceAnyLinkage ||
189            Linkage == LinkOnceODRLinkage ||
190            Linkage == CommonLinkage ||
191            Linkage == ExternalWeakLinkage ||
192            Linkage == LinkerPrivateWeakLinkage ||
193            Linkage == LinkerPrivateWeakDefAutoLinkage;
194   }
195 
hasExternalLinkage()196   bool hasExternalLinkage() const { return isExternalLinkage(Linkage); }
hasAvailableExternallyLinkage()197   bool hasAvailableExternallyLinkage() const {
198     return isAvailableExternallyLinkage(Linkage);
199   }
hasLinkOnceLinkage()200   bool hasLinkOnceLinkage() const {
201     return isLinkOnceLinkage(Linkage);
202   }
hasWeakLinkage()203   bool hasWeakLinkage() const {
204     return isWeakLinkage(Linkage);
205   }
hasAppendingLinkage()206   bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage); }
hasInternalLinkage()207   bool hasInternalLinkage() const { return isInternalLinkage(Linkage); }
hasPrivateLinkage()208   bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); }
hasLinkerPrivateLinkage()209   bool hasLinkerPrivateLinkage() const { return isLinkerPrivateLinkage(Linkage); }
hasLinkerPrivateWeakLinkage()210   bool hasLinkerPrivateWeakLinkage() const {
211     return isLinkerPrivateWeakLinkage(Linkage);
212   }
hasLinkerPrivateWeakDefAutoLinkage()213   bool hasLinkerPrivateWeakDefAutoLinkage() const {
214     return isLinkerPrivateWeakDefAutoLinkage(Linkage);
215   }
hasLocalLinkage()216   bool hasLocalLinkage() const { return isLocalLinkage(Linkage); }
hasDLLImportLinkage()217   bool hasDLLImportLinkage() const { return isDLLImportLinkage(Linkage); }
hasDLLExportLinkage()218   bool hasDLLExportLinkage() const { return isDLLExportLinkage(Linkage); }
hasExternalWeakLinkage()219   bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); }
hasCommonLinkage()220   bool hasCommonLinkage() const { return isCommonLinkage(Linkage); }
221 
setLinkage(LinkageTypes LT)222   void setLinkage(LinkageTypes LT) { Linkage = LT; }
getLinkage()223   LinkageTypes getLinkage() const { return Linkage; }
224 
mayBeOverridden()225   bool mayBeOverridden() const { return mayBeOverridden(Linkage); }
226 
isWeakForLinker()227   bool isWeakForLinker() const { return isWeakForLinker(Linkage); }
228 
229   /// copyAttributesFrom - copy all additional attributes (those not needed to
230   /// create a GlobalValue) from the GlobalValue Src to this one.
231   virtual void copyAttributesFrom(const GlobalValue *Src);
232 
233 /// @name Materialization
234 /// Materialization is used to construct functions only as they're needed. This
235 /// is useful to reduce memory usage in LLVM or parsing work done by the
236 /// BitcodeReader to load the Module.
237 /// @{
238 
239   /// isMaterializable - If this function's Module is being lazily streamed in
240   /// functions from disk or some other source, this method can be used to check
241   /// to see if the function has been read in yet or not.
242   bool isMaterializable() const;
243 
244   /// isDematerializable - Returns true if this function was loaded from a
245   /// GVMaterializer that's still attached to its Module and that knows how to
246   /// dematerialize the function.
247   bool isDematerializable() const;
248 
249   /// Materialize - make sure this GlobalValue is fully read.  If the module is
250   /// corrupt, this returns true and fills in the optional string with
251   /// information about the problem.  If successful, this returns false.
252   bool Materialize(std::string *ErrInfo = 0);
253 
254   /// Dematerialize - If this GlobalValue is read in, and if the GVMaterializer
255   /// supports it, release the memory for the function, and set it up to be
256   /// materialized lazily.  If !isDematerializable(), this method is a noop.
257   void Dematerialize();
258 
259 /// @}
260 
261   /// Override from Constant class.
262   virtual void destroyConstant();
263 
264   /// isDeclaration - Return true if the primary definition of this global
265   /// value is outside of the current translation unit.
266   bool isDeclaration() const;
267 
268   /// removeFromParent - This method unlinks 'this' from the containing module,
269   /// but does not delete it.
270   virtual void removeFromParent() = 0;
271 
272   /// eraseFromParent - This method unlinks 'this' from the containing module
273   /// and deletes it.
274   virtual void eraseFromParent() = 0;
275 
276   /// getParent - Get the module that this global value is contained inside
277   /// of...
getParent()278   inline Module *getParent() { return Parent; }
getParent()279   inline const Module *getParent() const { return Parent; }
280 
281   // Methods for support type inquiry through isa, cast, and dyn_cast:
classof(const GlobalValue *)282   static inline bool classof(const GlobalValue *) { return true; }
classof(const Value * V)283   static inline bool classof(const Value *V) {
284     return V->getValueID() == Value::FunctionVal ||
285            V->getValueID() == Value::GlobalVariableVal ||
286            V->getValueID() == Value::GlobalAliasVal;
287   }
288 };
289 
290 } // End llvm namespace
291 
292 #endif
293