LLVM 17.0.0git
IntrusiveRefCntPtr.h
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1//==- llvm/ADT/IntrusiveRefCntPtr.h - Smart Refcounting Pointer --*- C++ -*-==//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8///
9/// \file
10/// This file defines the RefCountedBase, ThreadSafeRefCountedBase, and
11/// IntrusiveRefCntPtr classes.
12///
13/// IntrusiveRefCntPtr is a smart pointer to an object which maintains a
14/// reference count. (ThreadSafe)RefCountedBase is a mixin class that adds a
15/// refcount member variable and methods for updating the refcount. An object
16/// that inherits from (ThreadSafe)RefCountedBase deletes itself when its
17/// refcount hits zero.
18///
19/// For example:
20///
21/// ```
22/// class MyClass : public RefCountedBase<MyClass> {};
23///
24/// void foo() {
25/// // Constructing an IntrusiveRefCntPtr increases the pointee's refcount
26/// // by 1 (from 0 in this case).
27/// IntrusiveRefCntPtr<MyClass> Ptr1(new MyClass());
28///
29/// // Copying an IntrusiveRefCntPtr increases the pointee's refcount by 1.
30/// IntrusiveRefCntPtr<MyClass> Ptr2(Ptr1);
31///
32/// // Constructing an IntrusiveRefCntPtr has no effect on the object's
33/// // refcount. After a move, the moved-from pointer is null.
34/// IntrusiveRefCntPtr<MyClass> Ptr3(std::move(Ptr1));
35/// assert(Ptr1 == nullptr);
36///
37/// // Clearing an IntrusiveRefCntPtr decreases the pointee's refcount by 1.
38/// Ptr2.reset();
39///
40/// // The object deletes itself when we return from the function, because
41/// // Ptr3's destructor decrements its refcount to 0.
42/// }
43/// ```
44///
45/// You can use IntrusiveRefCntPtr with isa<T>(), dyn_cast<T>(), etc.:
46///
47/// ```
48/// IntrusiveRefCntPtr<MyClass> Ptr(new MyClass());
49/// OtherClass *Other = dyn_cast<OtherClass>(Ptr); // Ptr.get() not required
50/// ```
51///
52/// IntrusiveRefCntPtr works with any class that
53///
54/// - inherits from (ThreadSafe)RefCountedBase,
55/// - has Retain() and Release() methods, or
56/// - specializes IntrusiveRefCntPtrInfo.
57///
58//===----------------------------------------------------------------------===//
59
60#ifndef LLVM_ADT_INTRUSIVEREFCNTPTR_H
61#define LLVM_ADT_INTRUSIVEREFCNTPTR_H
62
63#include <atomic>
64#include <cassert>
65#include <cstddef>
66#include <memory>
67
68namespace llvm {
69
70/// A CRTP mixin class that adds reference counting to a type.
71///
72/// The lifetime of an object which inherits from RefCountedBase is managed by
73/// calls to Release() and Retain(), which increment and decrement the object's
74/// refcount, respectively. When a Release() call decrements the refcount to 0,
75/// the object deletes itself.
76template <class Derived> class RefCountedBase {
77 mutable unsigned RefCount = 0;
78
79protected:
80 RefCountedBase() = default;
83
84#ifndef NDEBUG
86 assert(RefCount == 0 &&
87 "Destruction occurred when there are still references to this.");
88 }
89#else
90 // Default the destructor in release builds, A trivial destructor may enable
91 // better codegen.
92 ~RefCountedBase() = default;
93#endif
94
95public:
96 void Retain() const { ++RefCount; }
97
98 void Release() const {
99 assert(RefCount > 0 && "Reference count is already zero.");
100 if (--RefCount == 0)
101 delete static_cast<const Derived *>(this);
102 }
103};
104
105/// A thread-safe version of \c RefCountedBase.
106template <class Derived> class ThreadSafeRefCountedBase {
107 mutable std::atomic<int> RefCount{0};
108
109protected:
114
115#ifndef NDEBUG
117 assert(RefCount == 0 &&
118 "Destruction occurred when there are still references to this.");
119 }
120#else
121 // Default the destructor in release builds, A trivial destructor may enable
122 // better codegen.
123 ~ThreadSafeRefCountedBase() = default;
124#endif
125
126public:
127 void Retain() const { RefCount.fetch_add(1, std::memory_order_relaxed); }
128
129 void Release() const {
130 int NewRefCount = RefCount.fetch_sub(1, std::memory_order_acq_rel) - 1;
131 assert(NewRefCount >= 0 && "Reference count was already zero.");
132 if (NewRefCount == 0)
133 delete static_cast<const Derived *>(this);
134 }
135};
136
137/// Class you can specialize to provide custom retain/release functionality for
138/// a type.
139///
140/// Usually specializing this class is not necessary, as IntrusiveRefCntPtr
141/// works with any type which defines Retain() and Release() functions -- you
142/// can define those functions yourself if RefCountedBase doesn't work for you.
143///
144/// One case when you might want to specialize this type is if you have
145/// - Foo.h defines type Foo and includes Bar.h, and
146/// - Bar.h uses IntrusiveRefCntPtr<Foo> in inline functions.
147///
148/// Because Foo.h includes Bar.h, Bar.h can't include Foo.h in order to pull in
149/// the declaration of Foo. Without the declaration of Foo, normally Bar.h
150/// wouldn't be able to use IntrusiveRefCntPtr<Foo>, which wants to call
151/// T::Retain and T::Release.
152///
153/// To resolve this, Bar.h could include a third header, FooFwd.h, which
154/// forward-declares Foo and specializes IntrusiveRefCntPtrInfo<Foo>. Then
155/// Bar.h could use IntrusiveRefCntPtr<Foo>, although it still couldn't call any
156/// functions on Foo itself, because Foo would be an incomplete type.
157template <typename T> struct IntrusiveRefCntPtrInfo {
158 static void retain(T *obj) { obj->Retain(); }
159 static void release(T *obj) { obj->Release(); }
160};
161
162/// A smart pointer to a reference-counted object that inherits from
163/// RefCountedBase or ThreadSafeRefCountedBase.
164///
165/// This class increments its pointee's reference count when it is created, and
166/// decrements its refcount when it's destroyed (or is changed to point to a
167/// different object).
168template <typename T> class IntrusiveRefCntPtr {
169 T *Obj = nullptr;
170
171public:
173
174 explicit IntrusiveRefCntPtr() = default;
175 IntrusiveRefCntPtr(T *obj) : Obj(obj) { retain(); }
176 IntrusiveRefCntPtr(const IntrusiveRefCntPtr &S) : Obj(S.Obj) { retain(); }
177 IntrusiveRefCntPtr(IntrusiveRefCntPtr &&S) : Obj(S.Obj) { S.Obj = nullptr; }
178
179 template <class X,
180 std::enable_if_t<std::is_convertible<X *, T *>::value, bool> = true>
182 S.Obj = nullptr;
183 }
184
185 template <class X,
186 std::enable_if_t<std::is_convertible<X *, T *>::value, bool> = true>
187 IntrusiveRefCntPtr(std::unique_ptr<X> S) : Obj(S.release()) {
188 retain();
189 }
190
191 ~IntrusiveRefCntPtr() { release(); }
192
194 swap(S);
195 return *this;
196 }
197
198 T &operator*() const { return *Obj; }
199 T *operator->() const { return Obj; }
200 T *get() const { return Obj; }
201 explicit operator bool() const { return Obj; }
202
204 T *tmp = other.Obj;
205 other.Obj = Obj;
206 Obj = tmp;
207 }
208
209 void reset() {
210 release();
211 Obj = nullptr;
212 }
213
214 void resetWithoutRelease() { Obj = nullptr; }
215
216private:
217 void retain() {
218 if (Obj)
220 }
221
222 void release() {
223 if (Obj)
225 }
226
227 template <typename X> friend class IntrusiveRefCntPtr;
228};
229
230template <class T, class U>
232 const IntrusiveRefCntPtr<U> &B) {
233 return A.get() == B.get();
234}
235
236template <class T, class U>
238 const IntrusiveRefCntPtr<U> &B) {
239 return A.get() != B.get();
240}
241
242template <class T, class U>
243inline bool operator==(const IntrusiveRefCntPtr<T> &A, U *B) {
244 return A.get() == B;
245}
246
247template <class T, class U>
248inline bool operator!=(const IntrusiveRefCntPtr<T> &A, U *B) {
249 return A.get() != B;
250}
251
252template <class T, class U>
253inline bool operator==(T *A, const IntrusiveRefCntPtr<U> &B) {
254 return A == B.get();
255}
256
257template <class T, class U>
258inline bool operator!=(T *A, const IntrusiveRefCntPtr<U> &B) {
259 return A != B.get();
260}
261
262template <class T>
263bool operator==(std::nullptr_t, const IntrusiveRefCntPtr<T> &B) {
264 return !B;
265}
266
267template <class T>
268bool operator==(const IntrusiveRefCntPtr<T> &A, std::nullptr_t B) {
269 return B == A;
270}
271
272template <class T>
273bool operator!=(std::nullptr_t A, const IntrusiveRefCntPtr<T> &B) {
274 return !(A == B);
275}
276
277template <class T>
278bool operator!=(const IntrusiveRefCntPtr<T> &A, std::nullptr_t B) {
279 return !(A == B);
280}
281
282// Make IntrusiveRefCntPtr work with dyn_cast, isa, and the other idioms from
283// Casting.h.
284template <typename From> struct simplify_type;
285
286template <class T> struct simplify_type<IntrusiveRefCntPtr<T>> {
287 using SimpleType = T *;
288
290 return Val.get();
291 }
292};
293
294template <class T> struct simplify_type<const IntrusiveRefCntPtr<T>> {
295 using SimpleType = /*const*/ T *;
296
298 return Val.get();
299 }
300};
301
302/// Factory function for creating intrusive ref counted pointers.
303template <typename T, typename... Args>
305 return IntrusiveRefCntPtr<T>(new T(std::forward<Args>(A)...));
306}
307
308} // end namespace llvm
309
310#endif // LLVM_ADT_INTRUSIVEREFCNTPTR_H
aarch64 promote const
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
static GCRegistry::Add< ErlangGC > A("erlang", "erlang-compatible garbage collector")
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
#define T
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
A smart pointer to a reference-counted object that inherits from RefCountedBase or ThreadSafeRefCount...
IntrusiveRefCntPtr & operator=(IntrusiveRefCntPtr S)
IntrusiveRefCntPtr(IntrusiveRefCntPtr &&S)
IntrusiveRefCntPtr(const IntrusiveRefCntPtr &S)
void swap(IntrusiveRefCntPtr &other)
IntrusiveRefCntPtr(std::unique_ptr< X > S)
IntrusiveRefCntPtr(IntrusiveRefCntPtr< X > S)
A CRTP mixin class that adds reference counting to a type.
RefCountedBase(const RefCountedBase &)
RefCountedBase & operator=(const RefCountedBase &)=delete
RefCountedBase()=default
A thread-safe version of RefCountedBase.
ThreadSafeRefCountedBase(const ThreadSafeRefCountedBase &)
ThreadSafeRefCountedBase & operator=(const ThreadSafeRefCountedBase &)=delete
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
bool operator!=(uint64_t V1, const APInt &V2)
Definition: APInt.h:2040
IntrusiveRefCntPtr< T > makeIntrusiveRefCnt(Args &&...A)
Factory function for creating intrusive ref counted pointers.
bool operator==(const AddressRangeValuePair &LHS, const AddressRangeValuePair &RHS)
Class you can specialize to provide custom retain/release functionality for a type.
static SimpleType getSimplifiedValue(IntrusiveRefCntPtr< T > &Val)
static SimpleType getSimplifiedValue(const IntrusiveRefCntPtr< T > &Val)
Define a template that can be specialized by smart pointers to reflect the fact that they are automat...
Definition: Casting.h:34