GlobalValue.h revision 263508
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 24namespace llvm { 25 26class PointerType; 27class Module; 28 29class GlobalValue : public Constant { 30 GlobalValue(const GlobalValue &) LLVM_DELETED_FUNCTION; 31public: 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 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 LinkerPrivateLinkage, ///< Like Private, but linker removes. 44 LinkerPrivateWeakLinkage, ///< Like LinkerPrivate, but weak. 45 DLLImportLinkage, ///< Function to be imported from DLL 46 DLLExportLinkage, ///< Function to be accessible from DLL. 47 ExternalWeakLinkage,///< ExternalWeak linkage description. 48 CommonLinkage ///< Tentative definitions. 49 }; 50 51 /// @brief An enumeration for the kinds of visibility of global values. 52 enum VisibilityTypes { 53 DefaultVisibility = 0, ///< The GV is visible 54 HiddenVisibility, ///< The GV is hidden 55 ProtectedVisibility ///< The GV is protected 56 }; 57 58protected: 59 GlobalValue(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps, 60 LinkageTypes linkage, const Twine &Name) 61 : Constant(ty, vty, Ops, NumOps), Linkage(linkage), 62 Visibility(DefaultVisibility), Alignment(0), UnnamedAddr(0), Parent(0) { 63 setName(Name); 64 } 65 66 // Note: VC++ treats enums as signed, so an extra bit is required to prevent 67 // Linkage and Visibility from turning into negative values. 68 LinkageTypes Linkage : 5; // The linkage of this global 69 unsigned Visibility : 2; // The visibility style of this global 70 unsigned Alignment : 16; // Alignment of this symbol, must be power of two 71 unsigned UnnamedAddr : 1; // This value's address is not significant 72 Module *Parent; // The containing module. 73 std::string Section; // Section to emit this into, empty mean default 74public: 75 ~GlobalValue() { 76 removeDeadConstantUsers(); // remove any dead constants using this. 77 } 78 79 unsigned getAlignment() const { 80 return (1u << Alignment) >> 1; 81 } 82 void setAlignment(unsigned Align); 83 84 bool hasUnnamedAddr() const { return UnnamedAddr; } 85 void setUnnamedAddr(bool Val) { UnnamedAddr = Val; } 86 87 VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); } 88 bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; } 89 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; } 90 bool hasProtectedVisibility() const { 91 return Visibility == ProtectedVisibility; 92 } 93 void setVisibility(VisibilityTypes V) { Visibility = V; } 94 95 bool hasSection() const { return !Section.empty(); } 96 const std::string &getSection() const { return Section; } 97 void setSection(StringRef S) { Section = S; } 98 99 /// If the usage is empty (except transitively dead constants), then this 100 /// global value can be safely deleted since the destructor will 101 /// delete the dead constants as well. 102 /// @brief Determine if the usage of this global value is empty except 103 /// for transitively dead constants. 104 bool use_empty_except_constants(); 105 106 /// getType - Global values are always pointers. 107 inline PointerType *getType() const { 108 return cast<PointerType>(User::getType()); 109 } 110 111 static LinkageTypes getLinkOnceLinkage(bool ODR) { 112 return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage; 113 } 114 static LinkageTypes getWeakLinkage(bool ODR) { 115 return ODR ? WeakODRLinkage : WeakAnyLinkage; 116 } 117 118 static bool isExternalLinkage(LinkageTypes Linkage) { 119 return Linkage == ExternalLinkage; 120 } 121 static bool isAvailableExternallyLinkage(LinkageTypes Linkage) { 122 return Linkage == AvailableExternallyLinkage; 123 } 124 static bool isLinkOnceLinkage(LinkageTypes Linkage) { 125 return Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage; 126 } 127 static bool isWeakLinkage(LinkageTypes Linkage) { 128 return Linkage == WeakAnyLinkage || Linkage == WeakODRLinkage; 129 } 130 static bool isAppendingLinkage(LinkageTypes Linkage) { 131 return Linkage == AppendingLinkage; 132 } 133 static bool isInternalLinkage(LinkageTypes Linkage) { 134 return Linkage == InternalLinkage; 135 } 136 static bool isPrivateLinkage(LinkageTypes Linkage) { 137 return Linkage == PrivateLinkage; 138 } 139 static bool isLinkerPrivateLinkage(LinkageTypes Linkage) { 140 return Linkage == LinkerPrivateLinkage; 141 } 142 static bool isLinkerPrivateWeakLinkage(LinkageTypes Linkage) { 143 return Linkage == LinkerPrivateWeakLinkage; 144 } 145 static bool isLocalLinkage(LinkageTypes Linkage) { 146 return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage) || 147 isLinkerPrivateLinkage(Linkage) || isLinkerPrivateWeakLinkage(Linkage); 148 } 149 static bool isDLLImportLinkage(LinkageTypes Linkage) { 150 return Linkage == DLLImportLinkage; 151 } 152 static bool isDLLExportLinkage(LinkageTypes Linkage) { 153 return Linkage == DLLExportLinkage; 154 } 155 static bool isExternalWeakLinkage(LinkageTypes Linkage) { 156 return Linkage == ExternalWeakLinkage; 157 } 158 static bool isCommonLinkage(LinkageTypes Linkage) { 159 return Linkage == CommonLinkage; 160 } 161 162 /// isDiscardableIfUnused - Whether the definition of this global may be 163 /// discarded if it is not used in its compilation unit. 164 static bool isDiscardableIfUnused(LinkageTypes Linkage) { 165 return isLinkOnceLinkage(Linkage) || isLocalLinkage(Linkage); 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. 171 static bool mayBeOverridden(LinkageTypes Linkage) { 172 return Linkage == WeakAnyLinkage || 173 Linkage == LinkOnceAnyLinkage || 174 Linkage == CommonLinkage || 175 Linkage == ExternalWeakLinkage || 176 Linkage == LinkerPrivateWeakLinkage; 177 } 178 179 /// isWeakForLinker - Whether the definition of this global may be replaced at 180 /// link time. NB: Using this method outside of the code generators is almost 181 /// always a mistake: when working at the IR level use mayBeOverridden instead 182 /// as it knows about ODR semantics. 183 static bool isWeakForLinker(LinkageTypes Linkage) { 184 return Linkage == AvailableExternallyLinkage || 185 Linkage == WeakAnyLinkage || 186 Linkage == WeakODRLinkage || 187 Linkage == LinkOnceAnyLinkage || 188 Linkage == LinkOnceODRLinkage || 189 Linkage == CommonLinkage || 190 Linkage == ExternalWeakLinkage || 191 Linkage == LinkerPrivateWeakLinkage; 192 } 193 194 bool hasExternalLinkage() const { return isExternalLinkage(Linkage); } 195 bool hasAvailableExternallyLinkage() const { 196 return isAvailableExternallyLinkage(Linkage); 197 } 198 bool hasLinkOnceLinkage() const { 199 return isLinkOnceLinkage(Linkage); 200 } 201 bool hasWeakLinkage() const { 202 return isWeakLinkage(Linkage); 203 } 204 bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage); } 205 bool hasInternalLinkage() const { return isInternalLinkage(Linkage); } 206 bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); } 207 bool hasLinkerPrivateLinkage() const { return isLinkerPrivateLinkage(Linkage); } 208 bool hasLinkerPrivateWeakLinkage() const { 209 return isLinkerPrivateWeakLinkage(Linkage); 210 } 211 bool hasLocalLinkage() const { return isLocalLinkage(Linkage); } 212 bool hasDLLImportLinkage() const { return isDLLImportLinkage(Linkage); } 213 bool hasDLLExportLinkage() const { return isDLLExportLinkage(Linkage); } 214 bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); } 215 bool hasCommonLinkage() const { return isCommonLinkage(Linkage); } 216 217 void setLinkage(LinkageTypes LT) { Linkage = LT; } 218 LinkageTypes getLinkage() const { return Linkage; } 219 220 bool isDiscardableIfUnused() const { 221 return isDiscardableIfUnused(Linkage); 222 } 223 224 bool mayBeOverridden() const { return mayBeOverridden(Linkage); } 225 226 bool isWeakForLinker() const { return isWeakForLinker(Linkage); } 227 228 /// copyAttributesFrom - copy all additional attributes (those not needed to 229 /// create a GlobalValue) from the GlobalValue Src to this one. 230 virtual void copyAttributesFrom(const GlobalValue *Src); 231 232 /// getRealLinkageName - If special LLVM prefix that is used to inform the asm 233 /// printer to not emit usual symbol prefix before the symbol name is used 234 /// then return linkage name after skipping this special LLVM prefix. 235 static StringRef getRealLinkageName(StringRef Name) { 236 if (!Name.empty() && Name[0] == '\1') 237 return Name.substr(1); 238 return Name; 239 } 240 241/// @name Materialization 242/// Materialization is used to construct functions only as they're needed. This 243/// is useful to reduce memory usage in LLVM or parsing work done by the 244/// BitcodeReader to load the Module. 245/// @{ 246 247 /// isMaterializable - If this function's Module is being lazily streamed in 248 /// functions from disk or some other source, this method can be used to check 249 /// to see if the function has been read in yet or not. 250 bool isMaterializable() const; 251 252 /// isDematerializable - Returns true if this function was loaded from a 253 /// GVMaterializer that's still attached to its Module and that knows how to 254 /// dematerialize the function. 255 bool isDematerializable() const; 256 257 /// Materialize - make sure this GlobalValue is fully read. If the module is 258 /// corrupt, this returns true and fills in the optional string with 259 /// information about the problem. If successful, this returns false. 260 bool Materialize(std::string *ErrInfo = 0); 261 262 /// Dematerialize - If this GlobalValue is read in, and if the GVMaterializer 263 /// supports it, release the memory for the function, and set it up to be 264 /// materialized lazily. If !isDematerializable(), this method is a noop. 265 void Dematerialize(); 266 267/// @} 268 269 /// Override from Constant class. 270 virtual void destroyConstant(); 271 272 /// isDeclaration - Return true if the primary definition of this global 273 /// value is outside of the current translation unit. 274 bool isDeclaration() const; 275 276 /// removeFromParent - This method unlinks 'this' from the containing module, 277 /// but does not delete it. 278 virtual void removeFromParent() = 0; 279 280 /// eraseFromParent - This method unlinks 'this' from the containing module 281 /// and deletes it. 282 virtual void eraseFromParent() = 0; 283 284 /// getParent - Get the module that this global value is contained inside 285 /// of... 286 inline Module *getParent() { return Parent; } 287 inline const Module *getParent() const { return Parent; } 288 289 // Methods for support type inquiry through isa, cast, and dyn_cast: 290 static inline bool classof(const Value *V) { 291 return V->getValueID() == Value::FunctionVal || 292 V->getValueID() == Value::GlobalVariableVal || 293 V->getValueID() == Value::GlobalAliasVal; 294 } 295}; 296 297} // End llvm namespace 298 299#endif 300