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 std::string &Name = "",
54 Module *Parent = 0, bool ThreadLocal = false,
55 unsigned AddressSpace = 0);
56 /// GlobalVariable ctor - This creates a global and inserts it before the
57 /// specified other global.
58 GlobalVariable(const Type *Ty, bool isConstant, LinkageTypes Linkage,
59 Constant *Initializer, const std::string &Name,
60 GlobalVariable *InsertBefore, 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 /// getInitializer - Return the initializer for this global variable. It is
82 /// illegal to call this method if the global is external, because we cannot
83 /// tell what the value is initialized to!
85 inline /*const FIXME*/ Constant *getInitializer() const {
86 assert(hasInitializer() && "GV doesn't have initializer!");
87 return static_cast<Constant*>(Op<0>().get());
89 inline Constant *getInitializer() {
90 assert(hasInitializer() && "GV doesn't have initializer!");
91 return static_cast<Constant*>(Op<0>().get());
93 inline void setInitializer(Constant *CPV) {
95 if (hasInitializer()) {
100 if (!hasInitializer())
106 /// If the value is a global constant, its value is immutable throughout the
107 /// runtime execution of the program. Assigning a value into the constant
108 /// leads to undefined behavior.
110 bool isConstant() const { return isConstantGlobal; }
111 void setConstant(bool Val) { isConstantGlobal = Val; }
113 /// If the value is "Thread Local", its value isn't shared by the threads.
114 bool isThreadLocal() const { return isThreadLocalSymbol; }
115 void setThreadLocal(bool Val) { isThreadLocalSymbol = Val; }
117 /// copyAttributesFrom - copy all additional attributes (those not needed to
118 /// create a GlobalVariable) from the GlobalVariable Src to this one.
119 void copyAttributesFrom(const GlobalValue *Src);
121 /// removeFromParent - This method unlinks 'this' from the containing module,
122 /// but does not delete it.
124 virtual void removeFromParent();
126 /// eraseFromParent - This method unlinks 'this' from the containing module
129 virtual void eraseFromParent();
131 /// Override Constant's implementation of this method so we can
132 /// replace constant initializers.
133 virtual void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U);
135 // Methods for support type inquiry through isa, cast, and dyn_cast:
136 static inline bool classof(const GlobalVariable *) { return true; }
137 static inline bool classof(const Value *V) {
138 return V->getValueID() == Value::GlobalVariableVal;
143 struct OperandTraits<GlobalVariable> : OptionalOperandTraits<> {
146 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GlobalVariable, Value)
148 } // End llvm namespace