LLVM  15.0.0git
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 
68 namespace 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.
76 template <class Derived> class RefCountedBase {
77  mutable unsigned RefCount = 0;
78 
79 protected:
80  RefCountedBase() = default;
82  RefCountedBase &operator=(const RefCountedBase &) = delete;
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 
95 public:
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.
106 template <class Derived> class ThreadSafeRefCountedBase {
107  mutable std::atomic<int> RefCount{0};
108 
109 protected:
110  ThreadSafeRefCountedBase() = default;
113  operator=(const ThreadSafeRefCountedBase &) = delete;
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 
126 public:
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.
157 template <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).
168 template <typename T> class IntrusiveRefCntPtr {
169  T *Obj = nullptr;
170 
171 public:
172  using element_type = T;
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 
203  void swap(IntrusiveRefCntPtr &other) {
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 
216 private:
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 
230 template <class T, class U>
231 inline bool operator==(const IntrusiveRefCntPtr<T> &A,
232  const IntrusiveRefCntPtr<U> &B) {
233  return A.get() == B.get();
234 }
235 
236 template <class T, class U>
237 inline bool operator!=(const IntrusiveRefCntPtr<T> &A,
238  const IntrusiveRefCntPtr<U> &B) {
239  return A.get() != B.get();
240 }
241 
242 template <class T, class U>
243 inline bool operator==(const IntrusiveRefCntPtr<T> &A, U *B) {
244  return A.get() == B;
245 }
246 
247 template <class T, class U>
248 inline bool operator!=(const IntrusiveRefCntPtr<T> &A, U *B) {
249  return A.get() != B;
250 }
251 
252 template <class T, class U>
253 inline bool operator==(T *A, const IntrusiveRefCntPtr<U> &B) {
254  return A == B.get();
255 }
256 
257 template <class T, class U>
258 inline bool operator!=(T *A, const IntrusiveRefCntPtr<U> &B) {
259  return A != B.get();
260 }
261 
262 template <class T>
263 bool operator==(std::nullptr_t, const IntrusiveRefCntPtr<T> &B) {
264  return !B;
265 }
266 
267 template <class T>
268 bool operator==(const IntrusiveRefCntPtr<T> &A, std::nullptr_t B) {
269  return B == A;
270 }
271 
272 template <class T>
273 bool operator!=(std::nullptr_t A, const IntrusiveRefCntPtr<T> &B) {
274  return !(A == B);
275 }
276 
277 template <class T>
278 bool 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.
284 template <typename From> struct simplify_type;
285 
286 template <class T> struct simplify_type<IntrusiveRefCntPtr<T>> {
287  using SimpleType = T *;
288 
290  return Val.get();
291  }
292 };
293 
294 template <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.
303 template <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
llvm::IntrusiveRefCntPtr::get
T * get() const
Definition: IntrusiveRefCntPtr.h:200
llvm
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:17
llvm::RefCountedBase::RefCountedBase
RefCountedBase()=default
llvm::IntrusiveRefCntPtr::reset
void reset()
Definition: IntrusiveRefCntPtr.h:209
llvm::IntrusiveRefCntPtr::IntrusiveRefCntPtr
friend class IntrusiveRefCntPtr
Definition: IntrusiveRefCntPtr.h:227
llvm::ThreadSafeRefCountedBase::~ThreadSafeRefCountedBase
~ThreadSafeRefCountedBase()
Definition: IntrusiveRefCntPtr.h:116
llvm::operator!=
bool operator!=(uint64_t V1, const APInt &V2)
Definition: APInt.h:2004
llvm::ThreadSafeRefCountedBase::Retain
void Retain() const
Definition: IntrusiveRefCntPtr.h:127
T
#define T
Definition: Mips16ISelLowering.cpp:341
tmp
alloca< 16 x float >, align 16 %tmp2=alloca< 16 x float >, align 16 store< 16 x float > %A,< 16 x float > *%tmp %s=bitcast< 16 x float > *%tmp to i8 *%s2=bitcast< 16 x float > *%tmp2 to i8 *call void @llvm.memcpy.i64(i8 *%s, i8 *%s2, i64 64, i32 16) %R=load< 16 x float > *%tmp2 ret< 16 x float > %R } declare void @llvm.memcpy.i64(i8 *nocapture, i8 *nocapture, i64, i32) nounwind which compiles to:_foo:subl $140, %esp movaps %xmm3, 112(%esp) movaps %xmm2, 96(%esp) movaps %xmm1, 80(%esp) movaps %xmm0, 64(%esp) movl 60(%esp), %eax movl %eax, 124(%esp) movl 56(%esp), %eax movl %eax, 120(%esp) movl 52(%esp), %eax< many many more 32-bit copies > movaps(%esp), %xmm0 movaps 16(%esp), %xmm1 movaps 32(%esp), %xmm2 movaps 48(%esp), %xmm3 addl $140, %esp ret On Nehalem, it may even be cheaper to just use movups when unaligned than to fall back to lower-granularity chunks. Implement processor-specific optimizations for parity with GCC on these processors. GCC does two optimizations:1. ix86_pad_returns inserts a noop before ret instructions if immediately preceded by a conditional branch or is the target of a jump. 2. ix86_avoid_jump_misspredicts inserts noops in cases where a 16-byte block of code contains more than 3 branches. The first one is done for all AMDs, Core2, and "Generic" The second one is done for:Atom, Pentium Pro, all AMDs, Pentium 4, Nocona, Core 2, and "Generic" Testcase:int x(int a) { return(a &0xf0)> >4 tmp
Definition: README.txt:1347
llvm::RefCountedBase
A CRTP mixin class that adds reference counting to a type.
Definition: IntrusiveRefCntPtr.h:76
llvm::IntrusiveRefCntPtr::IntrusiveRefCntPtr
IntrusiveRefCntPtr(IntrusiveRefCntPtr &&S)
Definition: IntrusiveRefCntPtr.h:177
llvm::IntrusiveRefCntPtr::operator=
IntrusiveRefCntPtr & operator=(IntrusiveRefCntPtr S)
Definition: IntrusiveRefCntPtr.h:193
llvm::IntrusiveRefCntPtr::IntrusiveRefCntPtr
IntrusiveRefCntPtr(const IntrusiveRefCntPtr &S)
Definition: IntrusiveRefCntPtr.h:176
llvm::makeIntrusiveRefCnt
IntrusiveRefCntPtr< T > makeIntrusiveRefCnt(Args &&...A)
Factory function for creating intrusive ref counted pointers.
Definition: IntrusiveRefCntPtr.h:304
llvm::IntrusiveRefCntPtr::swap
void swap(IntrusiveRefCntPtr &other)
Definition: IntrusiveRefCntPtr.h:203
llvm::simplify_type< const IntrusiveRefCntPtr< T > >::getSimplifiedValue
static SimpleType getSimplifiedValue(const IntrusiveRefCntPtr< T > &Val)
Definition: IntrusiveRefCntPtr.h:297
llvm::simplify_type
Define a template that can be specialized by smart pointers to reflect the fact that they are automat...
Definition: ilist_iterator.h:178
B
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
llvm::ThreadSafeRefCountedBase
A thread-safe version of RefCountedBase.
Definition: IntrusiveRefCntPtr.h:106
llvm::IntrusiveRefCntPtr::operator->
T * operator->() const
Definition: IntrusiveRefCntPtr.h:199
X
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
llvm::IntrusiveRefCntPtr::IntrusiveRefCntPtr
IntrusiveRefCntPtr(T *obj)
Definition: IntrusiveRefCntPtr.h:175
llvm::IntrusiveRefCntPtr::operator*
T & operator*() const
Definition: IntrusiveRefCntPtr.h:198
const
aarch64 promote const
Definition: AArch64PromoteConstant.cpp:232
llvm::RefCountedBase::operator=
RefCountedBase & operator=(const RefCountedBase &)=delete
assert
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
llvm::operator==
bool operator==(uint64_t V1, const APInt &V2)
Definition: APInt.h:2002
llvm::simplify_type< IntrusiveRefCntPtr< T > >::getSimplifiedValue
static SimpleType getSimplifiedValue(IntrusiveRefCntPtr< T > &Val)
Definition: IntrusiveRefCntPtr.h:289
llvm::IntrusiveRefCntPtrInfo::retain
static void retain(T *obj)
Definition: IntrusiveRefCntPtr.h:158
llvm::RefCountedBase::~RefCountedBase
~RefCountedBase()
Definition: IntrusiveRefCntPtr.h:85
A
* A
Definition: README_ALTIVEC.txt:89
llvm::IntrusiveRefCntPtrInfo
Class you can specialize to provide custom retain/release functionality for a type.
Definition: IntrusiveRefCntPtr.h:157
S
add sub stmia L5 ldr r0 bl L_printf $stub Instead of a and a wouldn t it be better to do three moves *Return an aggregate type is even return S
Definition: README.txt:210
llvm::RefCountedBase::RefCountedBase
RefCountedBase(const RefCountedBase &)
Definition: IntrusiveRefCntPtr.h:81
llvm::vfs::FileSystem
The virtual file system interface.
Definition: VirtualFileSystem.h:267
llvm::ThreadSafeRefCountedBase::ThreadSafeRefCountedBase
ThreadSafeRefCountedBase(const ThreadSafeRefCountedBase &)
Definition: IntrusiveRefCntPtr.h:111
llvm::simplify_type< IntrusiveRefCntPtr< T > >::SimpleType
T * SimpleType
Definition: IntrusiveRefCntPtr.h:287
llvm::IntrusiveRefCntPtr::~IntrusiveRefCntPtr
~IntrusiveRefCntPtr()
Definition: IntrusiveRefCntPtr.h:191
llvm::RefCountedBase::Retain
void Retain() const
Definition: IntrusiveRefCntPtr.h:96
llvm::ThreadSafeRefCountedBase::ThreadSafeRefCountedBase
ThreadSafeRefCountedBase()=default
llvm::simplify_type< const IntrusiveRefCntPtr< T > >::SimpleType
T * SimpleType
Definition: IntrusiveRefCntPtr.h:295
llvm::RefCountedBase::Release
void Release() const
Definition: IntrusiveRefCntPtr.h:98
llvm::IntrusiveRefCntPtr::IntrusiveRefCntPtr
IntrusiveRefCntPtr(std::unique_ptr< X > S)
Definition: IntrusiveRefCntPtr.h:187
llvm::IntrusiveRefCntPtrInfo::release
static void release(T *obj)
Definition: IntrusiveRefCntPtr.h:159
llvm::AMDGPU::HSAMD::Kernel::Key::Args
constexpr char Args[]
Key for Kernel::Metadata::mArgs.
Definition: AMDGPUMetadata.h:394
llvm::ThreadSafeRefCountedBase::Release
void Release() const
Definition: IntrusiveRefCntPtr.h:129
llvm::ThreadSafeRefCountedBase::operator=
ThreadSafeRefCountedBase & operator=(const ThreadSafeRefCountedBase &)=delete
llvm::IntrusiveRefCntPtr
A smart pointer to a reference-counted object that inherits from RefCountedBase or ThreadSafeRefCount...
Definition: IntrusiveRefCntPtr.h:168
llvm::IntrusiveRefCntPtr::IntrusiveRefCntPtr
IntrusiveRefCntPtr(IntrusiveRefCntPtr< X > S)
Definition: IntrusiveRefCntPtr.h:181
llvm::IntrusiveRefCntPtr::resetWithoutRelease
void resetWithoutRelease()
Definition: IntrusiveRefCntPtr.h:214