1 //===-- llvm/GlobalVariable.h - GlobalVariable class ------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the declaration of the GlobalVariable class, which
11 // represents a single global variable (or constant) in the VM.
13 // Global variables are constant pointers that refer to hunks of space that are
14 // allocated by either the VM, or by the linker in a static compiler. A global
15 // variable may have an intial value, which is copied into the executables .data
16 // area. Global Constants are required to have initializers.
18 //===----------------------------------------------------------------------===//
20 #ifndef LLVM_GLOBAL_VARIABLE_H
21 #define LLVM_GLOBAL_VARIABLE_H
23 #include "llvm/GlobalValue.h"
24 #include "llvm/OperandTraits.h"
25 #include "llvm/ADT/ilist_node.h"
31 template<typename ValueSubClass, typename ItemParentClass>
32 class SymbolTableListTraits;
34 class GlobalVariable : public GlobalValue, public ilist_node<GlobalVariable> {
35 friend class SymbolTableListTraits<GlobalVariable, Module>;
36 void *operator new(size_t, unsigned); // Do not implement
37 void operator=(const GlobalVariable &); // Do not implement
38 GlobalVariable(const GlobalVariable &); // Do not implement
40 void setParent(Module *parent);
42 bool isConstantGlobal : 1; // Is this a global constant?
43 bool isThreadLocalSymbol : 1; // Is this symbol "Thread Local"?
46 // allocate space for exactly one operand
47 void *operator new(size_t s) {
48 return User::operator new(s, 1);
50 /// GlobalVariable ctor - If a parent module is specified, the global is
51 /// automatically inserted into the end of the specified modules global list.
52 GlobalVariable(const Type *Ty, bool isConstant, LinkageTypes Linkage,
53 Constant *Initializer = 0, const Twine &Name = "",
54 bool ThreadLocal = false, unsigned AddressSpace = 0);
55 /// GlobalVariable ctor - This creates a global and inserts it before the
56 /// specified other global.
57 GlobalVariable(Module &M, const Type *Ty, bool isConstant,
58 LinkageTypes Linkage, Constant *Initializer,
60 GlobalVariable *InsertBefore = 0, bool ThreadLocal = false,
61 unsigned AddressSpace = 0);
64 NumOperands = 1; // FIXME: needed by operator delete
67 /// Provide fast operand accessors
68 DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
70 /// isDeclaration - Is this global variable lacking an initializer? If so,
71 /// the global variable is defined in some other translation unit, and is thus
72 /// only a declaration here.
73 virtual bool isDeclaration() const { return getNumOperands() == 0; }
75 /// hasInitializer - Unless a global variable isExternal(), it has an
76 /// initializer. The initializer for the global variable/constant is held by
77 /// Initializer if an initializer is specified.
79 inline bool hasInitializer() const { return !isDeclaration(); }
81 /// hasDefinitiveInitializer - Whether the global variable has an initializer,
82 /// and this is the initializer that will be used in the final executable.
83 inline bool hasDefinitiveInitializer() const {
84 return hasInitializer() &&
85 // The initializer of a global variable with weak linkage may change at
90 /// getInitializer - Return the initializer for this global variable. It is
91 /// illegal to call this method if the global is external, because we cannot
92 /// tell what the value is initialized to!
94 inline /*const FIXME*/ Constant *getInitializer() const {
95 assert(hasInitializer() && "GV doesn't have initializer!");
96 return static_cast<Constant*>(Op<0>().get());
98 inline Constant *getInitializer() {
99 assert(hasInitializer() && "GV doesn't have initializer!");
100 return static_cast<Constant*>(Op<0>().get());
102 /// setInitializer - Sets the initializer for this global variable, removing
103 /// any existing initializer if InitVal==NULL. If this GV has type T*, the
104 /// initializer must have type T.
105 void setInitializer(Constant *InitVal);
107 /// If the value is a global constant, its value is immutable throughout the
108 /// runtime execution of the program. Assigning a value into the constant
109 /// leads to undefined behavior.
111 bool isConstant() const { return isConstantGlobal; }
112 void setConstant(bool Val) { isConstantGlobal = Val; }
114 /// If the value is "Thread Local", its value isn't shared by the threads.
115 bool isThreadLocal() const { return isThreadLocalSymbol; }
116 void setThreadLocal(bool Val) { isThreadLocalSymbol = Val; }
118 /// copyAttributesFrom - copy all additional attributes (those not needed to
119 /// create a GlobalVariable) from the GlobalVariable Src to this one.
120 void copyAttributesFrom(const GlobalValue *Src);
122 /// removeFromParent - This method unlinks 'this' from the containing module,
123 /// but does not delete it.
125 virtual void removeFromParent();
127 /// eraseFromParent - This method unlinks 'this' from the containing module
130 virtual void eraseFromParent();
132 /// Override Constant's implementation of this method so we can
133 /// replace constant initializers.
134 virtual void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U);
136 // Methods for support type inquiry through isa, cast, and dyn_cast:
137 static inline bool classof(const GlobalVariable *) { return true; }
138 static inline bool classof(const Value *V) {
139 return V->getValueID() == Value::GlobalVariableVal;
144 struct OperandTraits<GlobalVariable> : public OptionalOperandTraits<> {
147 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GlobalVariable, Value)
149 } // End llvm namespace