src/llvm/include/llvm/IR/GlobalValue.h

   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 #include <system_error>
  24
  25 namespace llvm {
  26
  27 class Comdat;
  28 class PointerType;
  29 class Module;
  30
  31 class GlobalValue : public Constant {
  32   GlobalValue(const GlobalValue &) LLVM_DELETED_FUNCTION;
  33 public:
  34   /// @brief An enumeration for the kinds of linkage for global values.
  35   enum LinkageTypes {
  36     ExternalLinkage = 0,///< Externally visible function
  37     AvailableExternallyLinkage, ///< Available for inspection, not emission.
  38     LinkOnceAnyLinkage, ///< Keep one copy of function when linking (inline)
  39     LinkOnceODRLinkage, ///< Same, but only replaced by something equivalent.
  40     WeakAnyLinkage,     ///< Keep one copy of named function when linking (weak)
  41     WeakODRLinkage,     ///< Same, but only replaced by something equivalent.
  42     AppendingLinkage,   ///< Special purpose, only applies to global arrays
  43     InternalLinkage,    ///< Rename collisions when linking (static functions).
  44     PrivateLinkage,     ///< Like Internal, but omit from symbol table.
  45     ExternalWeakLinkage,///< ExternalWeak linkage description.
  46     CommonLinkage       ///< Tentative definitions.
  47   };
  48
  49   /// @brief An enumeration for the kinds of visibility of global values.
  50   enum VisibilityTypes {
  51     DefaultVisibility = 0,  ///< The GV is visible
  52     HiddenVisibility,       ///< The GV is hidden
  53     ProtectedVisibility     ///< The GV is protected
  54   };
  55
  56   /// @brief Storage classes of global values for PE targets.
  57   enum DLLStorageClassTypes {
  58     DefaultStorageClass   = 0,
  59     DLLImportStorageClass = 1, ///< Function to be imported from DLL
  60     DLLExportStorageClass = 2  ///< Function to be accessible from DLL.
  61   };
  62
  63 protected:
  64   GlobalValue(Type *Ty, ValueTy VTy, Use *Ops, unsigned NumOps,
  65               LinkageTypes Linkage, const Twine &Name)
  66       : Constant(Ty, VTy, Ops, NumOps), Linkage(Linkage),
  67         Visibility(DefaultVisibility), UnnamedAddr(0),
  68         DllStorageClass(DefaultStorageClass),
  69         ThreadLocal(NotThreadLocal), Parent(nullptr) {
  70     setName(Name);
  71   }
  72
  73   // Note: VC++ treats enums as signed, so an extra bit is required to prevent
  74   // Linkage and Visibility from turning into negative values.
  75   LinkageTypes Linkage : 5;   // The linkage of this global
  76   unsigned Visibility : 2;    // The visibility style of this global
  77   unsigned UnnamedAddr : 1;   // This value's address is not significant
  78   unsigned DllStorageClass : 2; // DLL storage class
  79
  80   unsigned ThreadLocal : 3; // Is this symbol "Thread Local", if so, what is
  81                             // the desired model?
  82
  83 private:
  84   // Give subclasses access to what otherwise would be wasted padding.
  85   // (19 + 3 + 2 + 1 + 2 + 5) == 32.
  86   unsigned SubClassData : 19;
  87 protected:
  88   static const unsigned GlobalValueSubClassDataBits = 19;
  89   unsigned getGlobalValueSubClassData() const {
  90     return SubClassData;
  91   }
  92   void setGlobalValueSubClassData(unsigned V) {
  93     assert(V < (1 << 19) && "It will not fit");
  94     SubClassData = V;
  95   }
  96
  97   Module *Parent;             // The containing module.
  98 public:
  99   enum ThreadLocalMode {
 100     NotThreadLocal = 0,
 101     GeneralDynamicTLSModel,
 102     LocalDynamicTLSModel,
 103     InitialExecTLSModel,
 104     LocalExecTLSModel
 105   };
 106
 107   ~GlobalValue() {
 108     removeDeadConstantUsers();   // remove any dead constants using this.
 109   }
 110
 111   unsigned getAlignment() const;
 112
 113   bool hasUnnamedAddr() const { return UnnamedAddr; }
 114   void setUnnamedAddr(bool Val) { UnnamedAddr = Val; }
 115
 116   bool hasComdat() const { return getComdat() != nullptr; }
 117   Comdat *getComdat();
 118   const Comdat *getComdat() const {
 119     return const_cast<GlobalValue *>(this)->getComdat();
 120   }
 121
 122   VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
 123   bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; }
 124   bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
 125   bool hasProtectedVisibility() const {
 126     return Visibility == ProtectedVisibility;
 127   }
 128   void setVisibility(VisibilityTypes V) {
 129     assert((!hasLocalLinkage() || V == DefaultVisibility) &&
 130            "local linkage requires default visibility");
 131     Visibility = V;
 132   }
 133
 134   /// If the value is "Thread Local", its value isn't shared by the threads.
 135   bool isThreadLocal() const { return getThreadLocalMode() != NotThreadLocal; }
 136   void setThreadLocal(bool Val) {
 137     setThreadLocalMode(Val ? GeneralDynamicTLSModel : NotThreadLocal);
 138   }
 139   void setThreadLocalMode(ThreadLocalMode Val) {
 140     assert(Val == NotThreadLocal || getValueID() != Value::FunctionVal);
 141     ThreadLocal = Val;
 142   }
 143   ThreadLocalMode getThreadLocalMode() const {
 144     return static_cast<ThreadLocalMode>(ThreadLocal);
 145   }
 146
 147   DLLStorageClassTypes getDLLStorageClass() const {
 148     return DLLStorageClassTypes(DllStorageClass);
 149   }
 150   bool hasDLLImportStorageClass() const {
 151     return DllStorageClass == DLLImportStorageClass;
 152   }
 153   bool hasDLLExportStorageClass() const {
 154     return DllStorageClass == DLLExportStorageClass;
 155   }
 156   void setDLLStorageClass(DLLStorageClassTypes C) { DllStorageClass = C; }
 157
 158   bool hasSection() const { return !StringRef(getSection()).empty(); }
 159   // It is unfortunate that we have to use "char *" in here since this is
 160   // always non NULL, but:
 161   // * The C API expects a null terminated string, so we cannot use StringRef.
 162   // * The C API expects us to own it, so we cannot use a std:string.
 163   // * For GlobalAliases we can fail to find the section and we have to
 164   //   return "", so we cannot use a "const std::string &".
 165   const char *getSection() const;
 166
 167   /// Global values are always pointers.
 168   inline PointerType *getType() const {
 169     return cast<PointerType>(User::getType());
 170   }
 171
 172   static LinkageTypes getLinkOnceLinkage(bool ODR) {
 173     return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;
 174   }
 175   static LinkageTypes getWeakLinkage(bool ODR) {
 176     return ODR ? WeakODRLinkage : WeakAnyLinkage;
 177   }
 178
 179   static bool isExternalLinkage(LinkageTypes Linkage) {
 180     return Linkage == ExternalLinkage;
 181   }
 182   static bool isAvailableExternallyLinkage(LinkageTypes Linkage) {
 183     return Linkage == AvailableExternallyLinkage;
 184   }
 185   static bool isLinkOnceODRLinkage(LinkageTypes Linkage) {
 186     return Linkage == LinkOnceODRLinkage;
 187   }
 188   static bool isLinkOnceLinkage(LinkageTypes Linkage) {
 189     return Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage;
 190   }
 191   static bool isWeakAnyLinkage(LinkageTypes Linkage) {
 192     return Linkage == WeakAnyLinkage;
 193   }
 194   static bool isWeakODRLinkage(LinkageTypes Linkage) {
 195     return Linkage == WeakODRLinkage;
 196   }
 197   static bool isWeakLinkage(LinkageTypes Linkage) {
 198     return isWeakAnyLinkage(Linkage) || isWeakODRLinkage(Linkage);
 199   }
 200   static bool isAppendingLinkage(LinkageTypes Linkage) {
 201     return Linkage == AppendingLinkage;
 202   }
 203   static bool isInternalLinkage(LinkageTypes Linkage) {
 204     return Linkage == InternalLinkage;
 205   }
 206   static bool isPrivateLinkage(LinkageTypes Linkage) {
 207     return Linkage == PrivateLinkage;
 208   }
 209   static bool isLocalLinkage(LinkageTypes Linkage) {
 210     return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage);
 211   }
 212   static bool isExternalWeakLinkage(LinkageTypes Linkage) {
 213     return Linkage == ExternalWeakLinkage;
 214   }
 215   static bool isCommonLinkage(LinkageTypes Linkage) {
 216     return Linkage == CommonLinkage;
 217   }
 218
 219   /// Whether the definition of this global may be discarded if it is not used
 220   /// in its compilation unit.
 221   static bool isDiscardableIfUnused(LinkageTypes Linkage) {
 222     return isLinkOnceLinkage(Linkage) || isLocalLinkage(Linkage);
 223   }
 224
 225   /// Whether the definition of this global may be replaced by something
 226   /// non-equivalent at link time. For example, if a function has weak linkage
 227   /// then the code defining it may be replaced by different code.
 228   static bool mayBeOverridden(LinkageTypes Linkage) {
 229     return Linkage == WeakAnyLinkage || Linkage == LinkOnceAnyLinkage ||
 230            Linkage == CommonLinkage || Linkage == ExternalWeakLinkage;
 231   }
 232
 233   /// Whether the definition of this global may be replaced at link time.  NB:
 234   /// Using this method outside of the code generators is almost always a
 235   /// mistake: when working at the IR level use mayBeOverridden instead as it
 236   /// knows about ODR semantics.
 237   static bool isWeakForLinker(LinkageTypes Linkage)  {
 238     return Linkage == AvailableExternallyLinkage || Linkage == WeakAnyLinkage ||
 239            Linkage == WeakODRLinkage || Linkage == LinkOnceAnyLinkage ||
 240            Linkage == LinkOnceODRLinkage || Linkage == CommonLinkage ||
 241            Linkage == ExternalWeakLinkage;
 242   }
 243
 244   bool hasExternalLinkage() const { return isExternalLinkage(Linkage); }
 245   bool hasAvailableExternallyLinkage() const {
 246     return isAvailableExternallyLinkage(Linkage);
 247   }
 248   bool hasLinkOnceLinkage() const {
 249     return isLinkOnceLinkage(Linkage);
 250   }
 251   bool hasLinkOnceODRLinkage() const { return isLinkOnceODRLinkage(Linkage); }
 252   bool hasWeakLinkage() const {
 253     return isWeakLinkage(Linkage);
 254   }
 255   bool hasWeakAnyLinkage() const {
 256     return isWeakAnyLinkage(Linkage);
 257   }
 258   bool hasWeakODRLinkage() const {
 259     return isWeakODRLinkage(Linkage);
 260   }
 261   bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage); }
 262   bool hasInternalLinkage() const { return isInternalLinkage(Linkage); }
 263   bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); }
 264   bool hasLocalLinkage() const { return isLocalLinkage(Linkage); }
 265   bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); }
 266   bool hasCommonLinkage() const { return isCommonLinkage(Linkage); }
 267
 268   void setLinkage(LinkageTypes LT) {
 269     if (isLocalLinkage(LT))
 270       Visibility = DefaultVisibility;
 271     Linkage = LT;
 272   }
 273   LinkageTypes getLinkage() const { return Linkage; }
 274
 275   bool isDiscardableIfUnused() const {
 276     return isDiscardableIfUnused(Linkage);
 277   }
 278
 279   bool mayBeOverridden() const { return mayBeOverridden(Linkage); }
 280
 281   bool isWeakForLinker() const { return isWeakForLinker(Linkage); }
 282
 283   /// Copy all additional attributes (those not needed to create a GlobalValue)
 284   /// from the GlobalValue Src to this one.
 285   virtual void copyAttributesFrom(const GlobalValue *Src);
 286
 287   /// If special LLVM prefix that is used to inform the asm printer to not emit
 288   /// usual symbol prefix before the symbol name is used then return linkage
 289   /// name after skipping this special LLVM prefix.
 290   static StringRef getRealLinkageName(StringRef Name) {
 291     if (!Name.empty() && Name[0] == '\1')
 292       return Name.substr(1);
 293     return Name;
 294   }
 295
 296 /// @name Materialization
 297 /// Materialization is used to construct functions only as they're needed. This
 298 /// is useful to reduce memory usage in LLVM or parsing work done by the
 299 /// BitcodeReader to load the Module.
 300 /// @{
 301
 302   /// If this function's Module is being lazily streamed in functions from disk
 303   /// or some other source, this method can be used to check to see if the
 304   /// function has been read in yet or not.
 305   bool isMaterializable() const;
 306
 307   /// Returns true if this function was loaded from a GVMaterializer that's
 308   /// still attached to its Module and that knows how to dematerialize the
 309   /// function.
 310   bool isDematerializable() const;
 311
 312   /// Make sure this GlobalValue is fully read. If the module is corrupt, this
 313   /// returns true and fills in the optional string with information about the
 314   /// problem.  If successful, this returns false.
 315   std::error_code materialize();
 316
 317   /// If this GlobalValue is read in, and if the GVMaterializer supports it,
 318   /// release the memory for the function, and set it up to be materialized
 319   /// lazily. If !isDematerializable(), this method is a noop.
 320   void Dematerialize();
 321
 322 /// @}
 323
 324   /// Override from Constant class.
 325   void destroyConstant() override;
 326
 327   /// Return true if the primary definition of this global value is outside of
 328   /// the current translation unit.
 329   bool isDeclaration() const;
 330
 331   bool isDeclarationForLinker() const {
 332     if (hasAvailableExternallyLinkage())
 333       return true;
 334
 335     return isDeclaration();
 336   }
 337
 338   /// This method unlinks 'this' from the containing module, but does not delete
 339   /// it.
 340   virtual void removeFromParent() = 0;
 341
 342   /// This method unlinks 'this' from the containing module and deletes it.
 343   virtual void eraseFromParent() = 0;
 344
 345   /// Get the module that this global value is contained inside of...
 346   inline Module *getParent() { return Parent; }
 347   inline const Module *getParent() const { return Parent; }
 348
 349   const DataLayout *getDataLayout() const;
 350
 351   // Methods for support type inquiry through isa, cast, and dyn_cast:
 352   static inline bool classof(const Value *V) {
 353     return V->getValueID() == Value::FunctionVal ||
 354            V->getValueID() == Value::GlobalVariableVal ||
 355            V->getValueID() == Value::GlobalAliasVal;
 356   }
 357 };
 358
 359 } // End llvm namespace
 360
 361 #endif