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1 : //===-- llvm/GlobalVariable.h - GlobalVariable class ------------*- C++ -*-===//
2 : //
3 : // The LLVM Compiler Infrastructure
4 : //
5 : // This file is distributed under the University of Illinois Open Source
6 : // License. See LICENSE.TXT for details.
7 : //
8 : //===----------------------------------------------------------------------===//
9 : //
10 : // This file contains the declaration of the GlobalVariable class, which
11 : // represents a single global variable (or constant) in the VM.
12 : //
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.
17 : //
18 : //===----------------------------------------------------------------------===//
19 :
20 : #ifndef LLVM_IR_GLOBALVARIABLE_H
21 : #define LLVM_IR_GLOBALVARIABLE_H
22 :
23 : #include "llvm/ADT/PointerUnion.h"
24 : #include "llvm/ADT/Twine.h"
25 : #include "llvm/ADT/ilist_node.h"
26 : #include "llvm/IR/Attributes.h"
27 : #include "llvm/IR/GlobalObject.h"
28 : #include "llvm/IR/OperandTraits.h"
29 : #include "llvm/IR/Value.h"
30 : #include <cassert>
31 : #include <cstddef>
32 :
33 : namespace llvm {
34 :
35 : class Constant;
36 : class Module;
37 :
38 : template <typename ValueSubClass> class SymbolTableListTraits;
39 : class DIGlobalVariable;
40 : class DIGlobalVariableExpression;
41 :
42 : class GlobalVariable : public GlobalObject, public ilist_node<GlobalVariable> {
43 : friend class SymbolTableListTraits<GlobalVariable>;
44 :
45 : AttributeSet Attrs;
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?
51 :
52 : public:
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;
68 :
69 263524 : ~GlobalVariable() {
70 131762 : dropAllReferences();
71 131762 : }
72 :
73 : // allocate space for exactly one operand
74 : void *operator new(size_t s) {
75 382311 : return User::operator new(s, 1);
76 : }
77 :
78 : // delete space for exactly one operand as created in the corresponding new operator
79 : void operator delete(void *ptr){
80 : assert(ptr != nullptr && "must not be nullptr");
81 : User *Obj = static_cast<User *>(ptr);
82 : // Number of operands can be set to 0 after construction and initialization. Make sure
83 : // that number of operands is reset to 1, as this is needed in User::operator delete
84 : Obj->setGlobalVariableNumOperands(1);
85 131717 : User::operator delete(Obj);
86 : }
87 :
88 : /// Provide fast operand accessors
89 : DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
90 :
91 : /// Definitions have initializers, declarations don't.
92 : ///
93 34689366 : inline bool hasInitializer() const { return !isDeclaration(); }
94 :
95 : /// hasDefinitiveInitializer - Whether the global variable has an initializer,
96 : /// and any other instances of the global (this can happen due to weak
97 : /// linkage) are guaranteed to have the same initializer.
98 : ///
99 : /// Note that if you want to transform a global, you must use
100 : /// hasUniqueInitializer() instead, because of the *_odr linkage type.
101 : ///
102 : /// Example:
103 : ///
104 : /// @a = global SomeType* null - Initializer is both definitive and unique.
105 : ///
106 : /// @b = global weak SomeType* null - Initializer is neither definitive nor
107 : /// unique.
108 : ///
109 : /// @c = global weak_odr SomeType* null - Initializer is definitive, but not
110 : /// unique.
111 20903450 : inline bool hasDefinitiveInitializer() const {
112 : return hasInitializer() &&
113 : // The initializer of a global variable may change to something arbitrary
114 : // at link time.
115 20903450 : !isInterposable() &&
116 : // The initializer of a global variable with the externally_initialized
117 : // marker may change at runtime before C++ initializers are evaluated.
118 20903450 : !isExternallyInitialized();
119 : }
120 :
121 : /// hasUniqueInitializer - Whether the global variable has an initializer, and
122 : /// any changes made to the initializer will turn up in the final executable.
123 : inline bool hasUniqueInitializer() const {
124 : return
125 : // We need to be sure this is the definition that will actually be used
126 1113 : isStrongDefinitionForLinker() &&
127 : // It is not safe to modify initializers of global variables with the
128 : // external_initializer marker since the value may be changed at runtime
129 : // before C++ initializers are evaluated.
130 : !isExternallyInitialized();
131 : }
132 :
133 : /// getInitializer - Return the initializer for this global variable. It is
134 : /// illegal to call this method if the global is external, because we cannot
135 : /// tell what the value is initialized to!
136 : ///
137 : inline const Constant *getInitializer() const {
138 : assert(hasInitializer() && "GV doesn't have initializer!");
139 1275527 : return static_cast<Constant*>(Op<0>().get());
140 : }
141 : inline Constant *getInitializer() {
142 : assert(hasInitializer() && "GV doesn't have initializer!");
143 477488 : return static_cast<Constant*>(Op<0>().get());
144 : }
145 : /// setInitializer - Sets the initializer for this global variable, removing
146 : /// any existing initializer if InitVal==NULL. If this GV has type T*, the
147 : /// initializer must have type T.
148 : void setInitializer(Constant *InitVal);
149 :
150 : /// If the value is a global constant, its value is immutable throughout the
151 : /// runtime execution of the program. Assigning a value into the constant
152 : /// leads to undefined behavior.
153 : ///
154 44181280 : bool isConstant() const { return isConstantGlobal; }
155 92655 : void setConstant(bool Val) { isConstantGlobal = Val; }
156 :
157 : bool isExternallyInitialized() const {
158 20876015 : return isExternallyInitializedConstant;
159 : }
160 : void setExternallyInitialized(bool Val) {
161 29991 : isExternallyInitializedConstant = Val;
162 : }
163 :
164 : /// copyAttributesFrom - copy all additional attributes (those not needed to
165 : /// create a GlobalVariable) from the GlobalVariable Src to this one.
166 : void copyAttributesFrom(const GlobalVariable *Src);
167 :
168 : /// removeFromParent - This method unlinks 'this' from the containing module,
169 : /// but does not delete it.
170 : ///
171 : void removeFromParent();
172 :
173 : /// eraseFromParent - This method unlinks 'this' from the containing module
174 : /// and deletes it.
175 : ///
176 : void eraseFromParent();
177 :
178 : /// Drop all references in preparation to destroy the GlobalVariable. This
179 : /// drops not only the reference to the initializer but also to any metadata.
180 : void dropAllReferences();
181 :
182 : /// Attach a DIGlobalVariableExpression.
183 : void addDebugInfo(DIGlobalVariableExpression *GV);
184 :
185 : /// Fill the vector with all debug info attachements.
186 : void getDebugInfo(SmallVectorImpl<DIGlobalVariableExpression *> &GVs) const;
187 :
188 : /// Add attribute to this global.
189 : void addAttribute(Attribute::AttrKind Kind) {
190 : Attrs = Attrs.addAttribute(getContext(), Kind);
191 : }
192 :
193 : /// Add attribute to this global.
194 44 : void addAttribute(StringRef Kind, StringRef Val = StringRef()) {
195 44 : Attrs = Attrs.addAttribute(getContext(), Kind, Val);
196 44 : }
197 :
198 : /// Return true if the attribute exists.
199 : bool hasAttribute(Attribute::AttrKind Kind) const {
200 : return Attrs.hasAttribute(Kind);
201 : }
202 :
203 : /// Return true if the attribute exists.
204 : bool hasAttribute(StringRef Kind) const {
205 : return Attrs.hasAttribute(Kind);
206 : }
207 :
208 : /// Return true if any attributes exist.
209 : bool hasAttributes() const {
210 16211 : return Attrs.hasAttributes();
211 : }
212 :
213 : /// Return the attribute object.
214 : Attribute getAttribute(Attribute::AttrKind Kind) const {
215 : return Attrs.getAttribute(Kind);
216 : }
217 :
218 : /// Return the attribute object.
219 : Attribute getAttribute(StringRef Kind) const {
220 : return Attrs.getAttribute(Kind);
221 : }
222 :
223 : /// Return the attribute set for this global
224 0 : AttributeSet getAttributes() const {
225 0 : return Attrs;
226 : }
227 :
228 : /// Return attribute set as list with index.
229 : /// FIXME: This may not be required once ValueEnumerators
230 : /// in bitcode-writer can enumerate attribute-set.
231 4426 : AttributeList getAttributesAsList(unsigned index) const {
232 4426 : if (!hasAttributes())
233 4402 : return AttributeList();
234 : std::pair<unsigned, AttributeSet> AS[1] = {{index, Attrs}};
235 24 : return AttributeList::get(getContext(), AS);
236 : }
237 :
238 : /// Set attribute list for this global
239 0 : void setAttributes(AttributeSet A) {
240 7758 : Attrs = A;
241 0 : }
242 :
243 : /// Check if section name is present
244 1702 : bool hasImplicitSection() const {
245 5080 : return getAttributes().hasAttribute("bss-section") ||
246 3377 : getAttributes().hasAttribute("data-section") ||
247 3350 : getAttributes().hasAttribute("rodata-section");
248 : }
249 :
250 : // Methods for support type inquiry through isa, cast, and dyn_cast:
251 : static bool classof(const Value *V) {
252 127312666 : return V->getValueID() == Value::GlobalVariableVal;
253 : }
254 : };
255 :
256 : template <>
257 : struct OperandTraits<GlobalVariable> :
258 : public OptionalOperandTraits<GlobalVariable> {
259 : };
260 :
261 293 : DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GlobalVariable, Value)
262 :
263 : } // end namespace llvm
264 :
265 : #endif // LLVM_IR_GLOBALVARIABLE_H
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