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_IR_GLOBALVALUE_H 19 #define LLVM_IR_GLOBALVALUE_H 20 21 #include "llvm/IR/Constant.h" 22 #include "llvm/IR/DerivedTypes.h" 23 24 namespace llvm { 25 26 class PointerType; 27 class Module; 28 29 class GlobalValue : public Constant { 30 GlobalValue(const GlobalValue &) LLVM_DELETED_FUNCTION; 31 public: 32 /// @brief An enumeration for the kinds of linkage for global values. 33 enum LinkageTypes { 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 LinkOnceODRAutoHideLinkage, ///< Like LinkOnceODRLinkage but addr not taken. 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 LinkerPrivateLinkage, ///< Like Private, but linker removes. 45 LinkerPrivateWeakLinkage, ///< Like LinkerPrivate, but weak. 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: 60 GlobalValue(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps, 61 LinkageTypes linkage, const Twine &Name) 62 : Constant(ty, vty, Ops, NumOps), Linkage(linkage), 63 Visibility(DefaultVisibility), Alignment(0), UnnamedAddr(0), Parent(0) { 64 setName(Name); 65 } 66 67 // Note: VC++ treats enums as signed, so an extra bit is required to prevent 68 // Linkage and Visibility from turning into negative values. 69 LinkageTypes Linkage : 5; // The linkage of this global 70 unsigned Visibility : 2; // The visibility style of this global 71 unsigned Alignment : 16; // Alignment of this symbol, must be power of two 72 unsigned UnnamedAddr : 1; // This value's address is not significant 73 Module *Parent; // The containing module. 74 std::string Section; // Section to emit this into, empty mean default 75 public: 76 ~GlobalValue() { 77 removeDeadConstantUsers(); // remove any dead constants using this. 78 } 79 80 unsigned getAlignment() const { 81 return (1u << Alignment) >> 1; 82 } 83 void setAlignment(unsigned Align); 84 85 bool hasUnnamedAddr() const { return UnnamedAddr; } 86 void setUnnamedAddr(bool Val) { UnnamedAddr = Val; } 87 88 VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); } 89 bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; } 90 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; } 91 bool hasProtectedVisibility() const { 92 return Visibility == ProtectedVisibility; 93 } 94 void setVisibility(VisibilityTypes V) { Visibility = V; } 95 96 bool hasSection() const { return !Section.empty(); } 97 const std::string &getSection() const { return Section; } 98 void setSection(StringRef S) { Section = S; } 99 100 /// If the usage is empty (except transitively dead constants), then this 101 /// global value can be safely deleted since the destructor will 102 /// delete the dead constants as well. 103 /// @brief Determine if the usage of this global value is empty except 104 /// for transitively dead constants. 105 bool use_empty_except_constants(); 106 107 /// getType - Global values are always pointers. 108 inline PointerType *getType() const { 109 return cast<PointerType>(User::getType()); 110 } 111 112 static LinkageTypes getLinkOnceLinkage(bool ODR) { 113 return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage; 114 } 115 static LinkageTypes getWeakLinkage(bool ODR) { 116 return ODR ? WeakODRLinkage : WeakAnyLinkage; 117 } 118 119 static bool isExternalLinkage(LinkageTypes Linkage) { 120 return Linkage == ExternalLinkage; 121 } 122 static bool isAvailableExternallyLinkage(LinkageTypes Linkage) { 123 return Linkage == AvailableExternallyLinkage; 124 } 125 static bool isLinkOnceLinkage(LinkageTypes Linkage) { 126 return Linkage == LinkOnceAnyLinkage || 127 Linkage == LinkOnceODRLinkage || 128 Linkage == LinkOnceODRAutoHideLinkage; 129 } 130 static bool isLinkOnceODRAutoHideLinkage(LinkageTypes Linkage) { 131 return Linkage == LinkOnceODRAutoHideLinkage; 132 } 133 static bool isWeakLinkage(LinkageTypes Linkage) { 134 return Linkage == WeakAnyLinkage || Linkage == WeakODRLinkage; 135 } 136 static bool isAppendingLinkage(LinkageTypes Linkage) { 137 return Linkage == AppendingLinkage; 138 } 139 static bool isInternalLinkage(LinkageTypes Linkage) { 140 return Linkage == InternalLinkage; 141 } 142 static bool isPrivateLinkage(LinkageTypes Linkage) { 143 return Linkage == PrivateLinkage; 144 } 145 static bool isLinkerPrivateLinkage(LinkageTypes Linkage) { 146 return Linkage == LinkerPrivateLinkage; 147 } 148 static bool isLinkerPrivateWeakLinkage(LinkageTypes Linkage) { 149 return Linkage == LinkerPrivateWeakLinkage; 150 } 151 static bool isLocalLinkage(LinkageTypes Linkage) { 152 return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage) || 153 isLinkerPrivateLinkage(Linkage) || isLinkerPrivateWeakLinkage(Linkage); 154 } 155 static bool isDLLImportLinkage(LinkageTypes Linkage) { 156 return Linkage == DLLImportLinkage; 157 } 158 static bool isDLLExportLinkage(LinkageTypes Linkage) { 159 return Linkage == DLLExportLinkage; 160 } 161 static bool isExternalWeakLinkage(LinkageTypes Linkage) { 162 return Linkage == ExternalWeakLinkage; 163 } 164 static bool isCommonLinkage(LinkageTypes Linkage) { 165 return Linkage == CommonLinkage; 166 } 167 168 /// isDiscardableIfUnused - Whether the definition of this global may be 169 /// discarded if it is not used in its compilation unit. 170 static bool isDiscardableIfUnused(LinkageTypes Linkage) { 171 return isLinkOnceLinkage(Linkage) || isLocalLinkage(Linkage); 172 } 173 174 /// mayBeOverridden - Whether the definition of this global may be replaced 175 /// by something non-equivalent at link time. For example, if a function has 176 /// weak linkage then the code defining it may be replaced by different code. 177 static bool mayBeOverridden(LinkageTypes Linkage) { 178 return Linkage == WeakAnyLinkage || 179 Linkage == LinkOnceAnyLinkage || 180 Linkage == CommonLinkage || 181 Linkage == ExternalWeakLinkage || 182 Linkage == LinkerPrivateWeakLinkage; 183 } 184 185 /// isWeakForLinker - Whether the definition of this global may be replaced at 186 /// link time. NB: Using this method outside of the code generators is almost 187 /// always a mistake: when working at the IR level use mayBeOverridden instead 188 /// as it knows about ODR semantics. 189 static bool isWeakForLinker(LinkageTypes Linkage) { 190 return Linkage == AvailableExternallyLinkage || 191 Linkage == WeakAnyLinkage || 192 Linkage == WeakODRLinkage || 193 Linkage == LinkOnceAnyLinkage || 194 Linkage == LinkOnceODRLinkage || 195 Linkage == LinkOnceODRAutoHideLinkage || 196 Linkage == CommonLinkage || 197 Linkage == ExternalWeakLinkage || 198 Linkage == LinkerPrivateWeakLinkage; 199 } 200 201 bool hasExternalLinkage() const { return isExternalLinkage(Linkage); } 202 bool hasAvailableExternallyLinkage() const { 203 return isAvailableExternallyLinkage(Linkage); 204 } 205 bool hasLinkOnceLinkage() const { 206 return isLinkOnceLinkage(Linkage); 207 } 208 bool hasLinkOnceODRAutoHideLinkage() const { 209 return isLinkOnceODRAutoHideLinkage(Linkage); 210 } 211 bool hasWeakLinkage() const { 212 return isWeakLinkage(Linkage); 213 } 214 bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage); } 215 bool hasInternalLinkage() const { return isInternalLinkage(Linkage); } 216 bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); } 217 bool hasLinkerPrivateLinkage() const { return isLinkerPrivateLinkage(Linkage); } 218 bool hasLinkerPrivateWeakLinkage() const { 219 return isLinkerPrivateWeakLinkage(Linkage); 220 } 221 bool hasLocalLinkage() const { return isLocalLinkage(Linkage); } 222 bool hasDLLImportLinkage() const { return isDLLImportLinkage(Linkage); } 223 bool hasDLLExportLinkage() const { return isDLLExportLinkage(Linkage); } 224 bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); } 225 bool hasCommonLinkage() const { return isCommonLinkage(Linkage); } 226 227 void setLinkage(LinkageTypes LT) { Linkage = LT; } 228 LinkageTypes getLinkage() const { return Linkage; } 229 230 bool isDiscardableIfUnused() const { 231 return isDiscardableIfUnused(Linkage); 232 } 233 234 bool mayBeOverridden() const { return mayBeOverridden(Linkage); } 235 236 bool isWeakForLinker() const { return isWeakForLinker(Linkage); } 237 238 /// copyAttributesFrom - copy all additional attributes (those not needed to 239 /// create a GlobalValue) from the GlobalValue Src to this one. 240 virtual void copyAttributesFrom(const GlobalValue *Src); 241 242 /// getRealLinkageName - If special LLVM prefix that is used to inform the asm 243 /// printer to not emit usual symbol prefix before the symbol name is used 244 /// then return linkage name after skipping this special LLVM prefix. 245 static StringRef getRealLinkageName(StringRef Name) { 246 if (!Name.empty() && Name[0] == '\1') 247 return Name.substr(1); 248 return Name; 249 } 250 251 /// @name Materialization 252 /// Materialization is used to construct functions only as they're needed. This 253 /// is useful to reduce memory usage in LLVM or parsing work done by the 254 /// BitcodeReader to load the Module. 255 /// @{ 256 257 /// isMaterializable - If this function's Module is being lazily streamed in 258 /// functions from disk or some other source, this method can be used to check 259 /// to see if the function has been read in yet or not. 260 bool isMaterializable() const; 261 262 /// isDematerializable - Returns true if this function was loaded from a 263 /// GVMaterializer that's still attached to its Module and that knows how to 264 /// dematerialize the function. 265 bool isDematerializable() const; 266 267 /// Materialize - make sure this GlobalValue is fully read. If the module is 268 /// corrupt, this returns true and fills in the optional string with 269 /// information about the problem. If successful, this returns false. 270 bool Materialize(std::string *ErrInfo = 0); 271 272 /// Dematerialize - If this GlobalValue is read in, and if the GVMaterializer 273 /// supports it, release the memory for the function, and set it up to be 274 /// materialized lazily. If !isDematerializable(), this method is a noop. 275 void Dematerialize(); 276 277 /// @} 278 279 /// Override from Constant class. 280 virtual void destroyConstant(); 281 282 /// isDeclaration - Return true if the primary definition of this global 283 /// value is outside of the current translation unit. 284 bool isDeclaration() const; 285 286 /// removeFromParent - This method unlinks 'this' from the containing module, 287 /// but does not delete it. 288 virtual void removeFromParent() = 0; 289 290 /// eraseFromParent - This method unlinks 'this' from the containing module 291 /// and deletes it. 292 virtual void eraseFromParent() = 0; 293 294 /// getParent - Get the module that this global value is contained inside 295 /// of... 296 inline Module *getParent() { return Parent; } 297 inline const Module *getParent() const { return Parent; } 298 299 // Methods for support type inquiry through isa, cast, and dyn_cast: 300 static inline bool classof(const Value *V) { 301 return V->getValueID() == Value::FunctionVal || 302 V->getValueID() == Value::GlobalVariableVal || 303 V->getValueID() == Value::GlobalAliasVal; 304 } 305 }; 306 307 } // End llvm namespace 308 309 #endif 310
