GlobalVariable.h revision 261991
1249259Sdim//===-- llvm/GlobalVariable.h - GlobalVariable class ------------*- C++ -*-===// 2249259Sdim// 3249259Sdim// The LLVM Compiler Infrastructure 4249259Sdim// 5249259Sdim// This file is distributed under the University of Illinois Open Source 6249259Sdim// License. See LICENSE.TXT for details. 7249259Sdim// 8249259Sdim//===----------------------------------------------------------------------===// 9249259Sdim// 10249259Sdim// This file contains the declaration of the GlobalVariable class, which 11249259Sdim// represents a single global variable (or constant) in the VM. 12249259Sdim// 13249259Sdim// Global variables are constant pointers that refer to hunks of space that are 14249259Sdim// allocated by either the VM, or by the linker in a static compiler. A global 15249259Sdim// variable may have an initial value, which is copied into the executables .data 16249259Sdim// area. Global Constants are required to have initializers. 17249259Sdim// 18249259Sdim//===----------------------------------------------------------------------===// 19249259Sdim 20249259Sdim#ifndef LLVM_IR_GLOBALVARIABLE_H 21249259Sdim#define LLVM_IR_GLOBALVARIABLE_H 22249259Sdim 23249259Sdim#include "llvm/ADT/Twine.h" 24249259Sdim#include "llvm/ADT/ilist_node.h" 25249259Sdim#include "llvm/IR/GlobalValue.h" 26249259Sdim#include "llvm/IR/OperandTraits.h" 27249259Sdim 28249259Sdimnamespace llvm { 29249259Sdim 30249259Sdimclass Module; 31249259Sdimclass Constant; 32249259Sdimtemplate<typename ValueSubClass, typename ItemParentClass> 33249259Sdim class SymbolTableListTraits; 34249259Sdim 35249259Sdimclass GlobalVariable : public GlobalValue, public ilist_node<GlobalVariable> { 36249259Sdim friend class SymbolTableListTraits<GlobalVariable, Module>; 37249259Sdim void *operator new(size_t, unsigned) LLVM_DELETED_FUNCTION; 38249259Sdim void operator=(const GlobalVariable &) LLVM_DELETED_FUNCTION; 39249259Sdim GlobalVariable(const GlobalVariable &) LLVM_DELETED_FUNCTION; 40249259Sdim 41249259Sdim void setParent(Module *parent); 42249259Sdim 43249259Sdim bool isConstantGlobal : 1; // Is this a global constant? 44249259Sdim unsigned threadLocalMode : 3; // Is this symbol "Thread Local", 45249259Sdim // if so, what is the desired 46249259Sdim // model? 47249259Sdim bool isExternallyInitializedConstant : 1; // Is this a global whose value 48249259Sdim // can change from its initial 49249259Sdim // value before global 50249259Sdim // initializers are run? 51249259Sdim 52249259Sdimpublic: 53249259Sdim // allocate space for exactly one operand 54249259Sdim void *operator new(size_t s) { 55249259Sdim return User::operator new(s, 1); 56249259Sdim } 57249259Sdim 58249259Sdim enum ThreadLocalMode { 59249259Sdim NotThreadLocal = 0, 60249259Sdim GeneralDynamicTLSModel, 61249259Sdim LocalDynamicTLSModel, 62249259Sdim InitialExecTLSModel, 63249259Sdim LocalExecTLSModel 64249259Sdim }; 65249259Sdim 66249259Sdim /// GlobalVariable ctor - If a parent module is specified, the global is 67249259Sdim /// automatically inserted into the end of the specified modules global list. 68249259Sdim GlobalVariable(Type *Ty, bool isConstant, LinkageTypes Linkage, 69249259Sdim Constant *Initializer = 0, const Twine &Name = "", 70249259Sdim ThreadLocalMode = NotThreadLocal, unsigned AddressSpace = 0, 71249259Sdim bool isExternallyInitialized = false); 72249259Sdim /// GlobalVariable ctor - This creates a global and inserts it before the 73249259Sdim /// specified other global. 74249259Sdim GlobalVariable(Module &M, Type *Ty, bool isConstant, 75249259Sdim LinkageTypes Linkage, Constant *Initializer, 76249259Sdim const Twine &Name = "", GlobalVariable *InsertBefore = 0, 77249259Sdim ThreadLocalMode = NotThreadLocal, unsigned AddressSpace = 0, 78249259Sdim bool isExternallyInitialized = false); 79249259Sdim 80249259Sdim ~GlobalVariable() { 81249259Sdim NumOperands = 1; // FIXME: needed by operator delete 82249259Sdim } 83249259Sdim 84249259Sdim /// Provide fast operand accessors 85249259Sdim DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value); 86249259Sdim 87261991Sdim /// Definitions have initializers, declarations don't. 88249259Sdim /// 89249259Sdim inline bool hasInitializer() const { return !isDeclaration(); } 90249259Sdim 91249259Sdim /// hasDefinitiveInitializer - Whether the global variable has an initializer, 92249259Sdim /// and any other instances of the global (this can happen due to weak 93249259Sdim /// linkage) are guaranteed to have the same initializer. 94249259Sdim /// 95249259Sdim /// Note that if you want to transform a global, you must use 96249259Sdim /// hasUniqueInitializer() instead, because of the *_odr linkage type. 97249259Sdim /// 98249259Sdim /// Example: 99249259Sdim /// 100249259Sdim /// @a = global SomeType* null - Initializer is both definitive and unique. 101249259Sdim /// 102249259Sdim /// @b = global weak SomeType* null - Initializer is neither definitive nor 103249259Sdim /// unique. 104249259Sdim /// 105249259Sdim /// @c = global weak_odr SomeType* null - Initializer is definitive, but not 106249259Sdim /// unique. 107249259Sdim inline bool hasDefinitiveInitializer() const { 108249259Sdim return hasInitializer() && 109249259Sdim // The initializer of a global variable with weak linkage may change at 110249259Sdim // link time. 111249259Sdim !mayBeOverridden() && 112249259Sdim // The initializer of a global variable with the externally_initialized 113249259Sdim // marker may change at runtime before C++ initializers are evaluated. 114249259Sdim !isExternallyInitialized(); 115249259Sdim } 116249259Sdim 117249259Sdim /// hasUniqueInitializer - Whether the global variable has an initializer, and 118249259Sdim /// any changes made to the initializer will turn up in the final executable. 119249259Sdim inline bool hasUniqueInitializer() const { 120249259Sdim return hasInitializer() && 121249259Sdim // It's not safe to modify initializers of global variables with weak 122249259Sdim // linkage, because the linker might choose to discard the initializer and 123249259Sdim // use the initializer from another instance of the global variable 124249259Sdim // instead. It is wrong to modify the initializer of a global variable 125249259Sdim // with *_odr linkage because then different instances of the global may 126249259Sdim // have different initializers, breaking the One Definition Rule. 127249259Sdim !isWeakForLinker() && 128249259Sdim // It is not safe to modify initializers of global variables with the 129249259Sdim // external_initializer marker since the value may be changed at runtime 130249259Sdim // before C++ initializers are evaluated. 131249259Sdim !isExternallyInitialized(); 132249259Sdim } 133249259Sdim 134249259Sdim /// getInitializer - Return the initializer for this global variable. It is 135249259Sdim /// illegal to call this method if the global is external, because we cannot 136249259Sdim /// tell what the value is initialized to! 137249259Sdim /// 138249259Sdim inline const Constant *getInitializer() const { 139249259Sdim assert(hasInitializer() && "GV doesn't have initializer!"); 140249259Sdim return static_cast<Constant*>(Op<0>().get()); 141249259Sdim } 142249259Sdim inline Constant *getInitializer() { 143249259Sdim assert(hasInitializer() && "GV doesn't have initializer!"); 144249259Sdim return static_cast<Constant*>(Op<0>().get()); 145249259Sdim } 146249259Sdim /// setInitializer - Sets the initializer for this global variable, removing 147249259Sdim /// any existing initializer if InitVal==NULL. If this GV has type T*, the 148249259Sdim /// initializer must have type T. 149249259Sdim void setInitializer(Constant *InitVal); 150249259Sdim 151249259Sdim /// If the value is a global constant, its value is immutable throughout the 152249259Sdim /// runtime execution of the program. Assigning a value into the constant 153249259Sdim /// leads to undefined behavior. 154249259Sdim /// 155249259Sdim bool isConstant() const { return isConstantGlobal; } 156249259Sdim void setConstant(bool Val) { isConstantGlobal = Val; } 157249259Sdim 158249259Sdim /// If the value is "Thread Local", its value isn't shared by the threads. 159249259Sdim bool isThreadLocal() const { return threadLocalMode != NotThreadLocal; } 160249259Sdim void setThreadLocal(bool Val) { 161249259Sdim threadLocalMode = Val ? GeneralDynamicTLSModel : NotThreadLocal; 162249259Sdim } 163249259Sdim void setThreadLocalMode(ThreadLocalMode Val) { threadLocalMode = Val; } 164249259Sdim ThreadLocalMode getThreadLocalMode() const { 165249259Sdim return static_cast<ThreadLocalMode>(threadLocalMode); 166249259Sdim } 167249259Sdim 168249259Sdim bool isExternallyInitialized() const { 169249259Sdim return isExternallyInitializedConstant; 170249259Sdim } 171249259Sdim void setExternallyInitialized(bool Val) { 172249259Sdim isExternallyInitializedConstant = Val; 173249259Sdim } 174249259Sdim 175249259Sdim /// copyAttributesFrom - copy all additional attributes (those not needed to 176249259Sdim /// create a GlobalVariable) from the GlobalVariable Src to this one. 177249259Sdim void copyAttributesFrom(const GlobalValue *Src); 178249259Sdim 179249259Sdim /// removeFromParent - This method unlinks 'this' from the containing module, 180249259Sdim /// but does not delete it. 181249259Sdim /// 182249259Sdim virtual void removeFromParent(); 183249259Sdim 184249259Sdim /// eraseFromParent - This method unlinks 'this' from the containing module 185249259Sdim /// and deletes it. 186249259Sdim /// 187249259Sdim virtual void eraseFromParent(); 188249259Sdim 189249259Sdim /// Override Constant's implementation of this method so we can 190249259Sdim /// replace constant initializers. 191249259Sdim virtual void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U); 192249259Sdim 193249259Sdim // Methods for support type inquiry through isa, cast, and dyn_cast: 194249259Sdim static inline bool classof(const Value *V) { 195249259Sdim return V->getValueID() == Value::GlobalVariableVal; 196249259Sdim } 197249259Sdim}; 198249259Sdim 199249259Sdimtemplate <> 200249259Sdimstruct OperandTraits<GlobalVariable> : 201249259Sdim public OptionalOperandTraits<GlobalVariable> { 202249259Sdim}; 203249259Sdim 204249259SdimDEFINE_TRANSPARENT_OPERAND_ACCESSORS(GlobalVariable, Value) 205249259Sdim 206249259Sdim} // End llvm namespace 207249259Sdim 208249259Sdim#endif 209