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"
32 template<typename ValueSubClass, typename ItemParentClass>
33 class SymbolTableListTraits;
35 class GlobalVariable : public GlobalValue, public ilist_node<GlobalVariable> {
36 friend class SymbolTableListTraits<GlobalVariable, Module>;
37 void *operator new(size_t, unsigned); // Do not implement
38 void operator=(const GlobalVariable &); // Do not implement
39 GlobalVariable(const GlobalVariable &); // Do not implement
41 void setParent(Module *parent);
43 bool isConstantGlobal : 1; // Is this a global constant?
44 bool isThreadLocalSymbol : 1; // Is this symbol "Thread Local"?
47 // allocate space for exactly one operand
48 void *operator new(size_t s) {
49 return User::operator new(s, 1);
51 /// GlobalVariable ctor - If a parent module is specified, the global is
52 /// automatically inserted into the end of the specified modules global list.
53 GlobalVariable(LLVMContext &Context, const Type *Ty, bool isConstant,
55 Constant *Initializer = 0, const std::string &Name = "",
56 bool ThreadLocal = false, unsigned AddressSpace = 0);
57 /// GlobalVariable ctor - This creates a global and inserts it before the
58 /// specified other global.
59 GlobalVariable(Module &M, const Type *Ty, bool isConstant,
60 LinkageTypes Linkage, Constant *Initializer,
61 const std::string &Name,
62 GlobalVariable *InsertBefore = 0, bool ThreadLocal = false,
63 unsigned AddressSpace = 0);
66 NumOperands = 1; // FIXME: needed by operator delete
69 /// Provide fast operand accessors
70 DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
72 /// isDeclaration - Is this global variable lacking an initializer? If so,
73 /// the global variable is defined in some other translation unit, and is thus
74 /// only a declaration here.
75 virtual bool isDeclaration() const { return getNumOperands() == 0; }
77 /// hasInitializer - Unless a global variable isExternal(), it has an
78 /// initializer. The initializer for the global variable/constant is held by
79 /// Initializer if an initializer is specified.
81 inline bool hasInitializer() const { return !isDeclaration(); }
83 /// hasDefinitiveInitializer - Whether the global variable has an initializer,
84 /// and this is the initializer that will be used in the final executable.
85 inline bool hasDefinitiveInitializer() const {
86 return hasInitializer() &&
87 // The initializer of a global variable with weak linkage may change at
92 /// getInitializer - Return the initializer for this global variable. It is
93 /// illegal to call this method if the global is external, because we cannot
94 /// tell what the value is initialized to!
96 inline /*const FIXME*/ Constant *getInitializer() const {
97 assert(hasInitializer() && "GV doesn't have initializer!");
98 return static_cast<Constant*>(Op<0>().get());
100 inline Constant *getInitializer() {
101 assert(hasInitializer() && "GV doesn't have initializer!");
102 return static_cast<Constant*>(Op<0>().get());
104 inline void setInitializer(Constant *CPV) {
106 if (hasInitializer()) {
111 if (!hasInitializer())
117 /// If the value is a global constant, its value is immutable throughout the
118 /// runtime execution of the program. Assigning a value into the constant
119 /// leads to undefined behavior.
121 bool isConstant() const { return isConstantGlobal; }
122 void setConstant(bool Val) { isConstantGlobal = Val; }
124 /// If the value is "Thread Local", its value isn't shared by the threads.
125 bool isThreadLocal() const { return isThreadLocalSymbol; }
126 void setThreadLocal(bool Val) { isThreadLocalSymbol = Val; }
128 /// copyAttributesFrom - copy all additional attributes (those not needed to
129 /// create a GlobalVariable) from the GlobalVariable Src to this one.
130 void copyAttributesFrom(const GlobalValue *Src);
132 /// removeFromParent - This method unlinks 'this' from the containing module,
133 /// but does not delete it.
135 virtual void removeFromParent();
137 /// eraseFromParent - This method unlinks 'this' from the containing module
140 virtual void eraseFromParent();
142 /// Override Constant's implementation of this method so we can
143 /// replace constant initializers.
144 virtual void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U);
146 // Methods for support type inquiry through isa, cast, and dyn_cast:
147 static inline bool classof(const GlobalVariable *) { return true; }
148 static inline bool classof(const Value *V) {
149 return V->getValueID() == Value::GlobalVariableVal;
154 struct OperandTraits<GlobalVariable> : OptionalOperandTraits<> {
157 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GlobalVariable, Value)
159 } // End llvm namespace