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 initial value, which is copied into the executables .data
16 // area. Global Constants are required to have initializers.
18 //===----------------------------------------------------------------------===//
20 #ifndef LLVM_IR_GLOBALVARIABLE_H
21 #define LLVM_IR_GLOBALVARIABLE_H
23 #include "llvm/ADT/PointerUnion.h"
24 #include "llvm/ADT/Twine.h"
25 #include "llvm/ADT/ilist_node.h"
26 #include "llvm/IR/GlobalObject.h"
27 #include "llvm/IR/Attributes.h"
28 #include "llvm/IR/OperandTraits.h"
29 #include "llvm/IR/Value.h"
38 template <typename ValueSubClass> class SymbolTableListTraits;
39 class DIGlobalVariable;
40 class DIGlobalVariableExpression;
42 class GlobalVariable : public GlobalObject, public ilist_node<GlobalVariable> {
43 friend class SymbolTableListTraits<GlobalVariable>;
46 bool isConstantGlobal : 1; // Is this a global constant?
47 bool isExternallyInitializedConstant : 1; // Is this a global whose value
48 // can change from its initial
49 // value before global
50 // initializers are run?
53 /// GlobalVariable ctor - If a parent module is specified, the global is
54 /// automatically inserted into the end of the specified modules global list.
55 GlobalVariable(Type *Ty, bool isConstant, LinkageTypes Linkage,
56 Constant *Initializer = nullptr, const Twine &Name = "",
57 ThreadLocalMode = NotThreadLocal, unsigned AddressSpace = 0,
58 bool isExternallyInitialized = false);
59 /// GlobalVariable ctor - This creates a global and inserts it before the
60 /// specified other global.
61 GlobalVariable(Module &M, Type *Ty, bool isConstant,
62 LinkageTypes Linkage, Constant *Initializer,
63 const Twine &Name = "", GlobalVariable *InsertBefore = nullptr,
64 ThreadLocalMode = NotThreadLocal, unsigned AddressSpace = 0,
65 bool isExternallyInitialized = false);
66 GlobalVariable(const GlobalVariable &) = delete;
67 GlobalVariable &operator=(const GlobalVariable &) = delete;
72 // FIXME: needed by operator delete
73 setGlobalVariableNumOperands(1);
76 // allocate space for exactly one operand
77 void *operator new(size_t s) {
78 return User::operator new(s, 1);
81 void *operator new(size_t, unsigned) = delete;
83 /// Provide fast operand accessors
84 DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
86 /// Definitions have initializers, declarations don't.
88 inline bool hasInitializer() const { return !isDeclaration(); }
90 /// hasDefinitiveInitializer - Whether the global variable has an initializer,
91 /// and any other instances of the global (this can happen due to weak
92 /// linkage) are guaranteed to have the same initializer.
94 /// Note that if you want to transform a global, you must use
95 /// hasUniqueInitializer() instead, because of the *_odr linkage type.
99 /// @a = global SomeType* null - Initializer is both definitive and unique.
101 /// @b = global weak SomeType* null - Initializer is neither definitive nor
104 /// @c = global weak_odr SomeType* null - Initializer is definitive, but not
106 inline bool hasDefinitiveInitializer() const {
107 return hasInitializer() &&
108 // The initializer of a global variable may change to something arbitrary
111 // The initializer of a global variable with the externally_initialized
112 // marker may change at runtime before C++ initializers are evaluated.
113 !isExternallyInitialized();
116 /// hasUniqueInitializer - Whether the global variable has an initializer, and
117 /// any changes made to the initializer will turn up in the final executable.
118 inline bool hasUniqueInitializer() const {
120 // We need to be sure this is the definition that will actually be used
121 isStrongDefinitionForLinker() &&
122 // It is not safe to modify initializers of global variables with the
123 // external_initializer marker since the value may be changed at runtime
124 // before C++ initializers are evaluated.
125 !isExternallyInitialized();
128 /// getInitializer - Return the initializer for this global variable. It is
129 /// illegal to call this method if the global is external, because we cannot
130 /// tell what the value is initialized to!
132 inline const Constant *getInitializer() const {
133 assert(hasInitializer() && "GV doesn't have initializer!");
134 return static_cast<Constant*>(Op<0>().get());
136 inline Constant *getInitializer() {
137 assert(hasInitializer() && "GV doesn't have initializer!");
138 return static_cast<Constant*>(Op<0>().get());
140 /// setInitializer - Sets the initializer for this global variable, removing
141 /// any existing initializer if InitVal==NULL. If this GV has type T*, the
142 /// initializer must have type T.
143 void setInitializer(Constant *InitVal);
145 /// If the value is a global constant, its value is immutable throughout the
146 /// runtime execution of the program. Assigning a value into the constant
147 /// leads to undefined behavior.
149 bool isConstant() const { return isConstantGlobal; }
150 void setConstant(bool Val) { isConstantGlobal = Val; }
152 bool isExternallyInitialized() const {
153 return isExternallyInitializedConstant;
155 void setExternallyInitialized(bool Val) {
156 isExternallyInitializedConstant = Val;
159 /// copyAttributesFrom - copy all additional attributes (those not needed to
160 /// create a GlobalVariable) from the GlobalVariable Src to this one.
161 void copyAttributesFrom(const GlobalVariable *Src);
163 /// removeFromParent - This method unlinks 'this' from the containing module,
164 /// but does not delete it.
166 void removeFromParent();
168 /// eraseFromParent - This method unlinks 'this' from the containing module
171 void eraseFromParent();
173 /// Drop all references in preparation to destroy the GlobalVariable. This
174 /// drops not only the reference to the initializer but also to any metadata.
175 void dropAllReferences();
177 /// Attach a DIGlobalVariableExpression.
178 void addDebugInfo(DIGlobalVariableExpression *GV);
180 /// Fill the vector with all debug info attachements.
181 void getDebugInfo(SmallVectorImpl<DIGlobalVariableExpression *> &GVs) const;
183 /// Add attribute to this global.
184 void addAttribute(Attribute::AttrKind Kind) {
185 Attrs = Attrs.addAttribute(getContext(), Kind);
188 /// Add attribute to this global.
189 void addAttribute(StringRef Kind, StringRef Val = StringRef()) {
190 Attrs = Attrs.addAttribute(getContext(), Kind, Val);
193 /// Return true if the attribute exists.
194 bool hasAttribute(Attribute::AttrKind Kind) const {
195 return Attrs.hasAttribute(Kind);
198 /// Return true if the attribute exists.
199 bool hasAttribute(StringRef Kind) const {
200 return Attrs.hasAttribute(Kind);
203 /// Return true if any attributes exist.
204 bool hasAttributes() const {
205 return Attrs.hasAttributes();
208 /// Return the attribute object.
209 Attribute getAttribute(Attribute::AttrKind Kind) const {
210 return Attrs.getAttribute(Kind);
213 /// Return the attribute object.
214 Attribute getAttribute(StringRef Kind) const {
215 return Attrs.getAttribute(Kind);
218 /// Return the attribute set for this global
219 AttributeSet getAttributes() const {
223 /// Return attribute set as list with index.
224 /// FIXME: This may not be required once ValueEnumerators
225 /// in bitcode-writer can enumerate attribute-set.
226 AttributeList getAttributesAsList(unsigned index) const {
227 if (!hasAttributes())
228 return AttributeList();
229 std::pair<unsigned, AttributeSet> AS[1] = {{index, Attrs}};
230 return AttributeList::get(getContext(), AS);
233 /// Set attribute list for this global
234 void setAttributes(AttributeSet A) {
238 // Methods for support type inquiry through isa, cast, and dyn_cast:
239 static inline bool classof(const Value *V) {
240 return V->getValueID() == Value::GlobalVariableVal;
245 struct OperandTraits<GlobalVariable> :
246 public OptionalOperandTraits<GlobalVariable> {
249 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GlobalVariable, Value)
251 } // end namespace llvm
253 #endif // LLVM_IR_GLOBALVARIABLE_H