LCOV - code coverage report
Current view: top level - include/llvm/ADT - IntrusiveRefCntPtr.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 49 49 100.0 %
Date: 2017-09-14 15:23:50 Functions: 15 16 93.8 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //==- llvm/ADT/IntrusiveRefCntPtr.h - Smart Refcounting Pointer --*- 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 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             : //   class MyClass : public RefCountedBase<MyClass> {};
      22             : //
      23             : //   void foo() {
      24             : //     // Constructing an IntrusiveRefCntPtr increases the pointee's refcount by
      25             : //     // 1 (from 0 in this case).
      26             : //     IntrusiveRefCntPtr<MyClass> Ptr1(new MyClass());
      27             : //
      28             : //     // Copying an IntrusiveRefCntPtr increases the pointee's refcount by 1.
      29             : //     IntrusiveRefCntPtr<MyClass> Ptr2(Ptr1);
      30             : //
      31             : //     // Constructing an IntrusiveRefCntPtr has no effect on the object's
      32             : //     // refcount.  After a move, the moved-from pointer is null.
      33             : //     IntrusiveRefCntPtr<MyClass> Ptr3(std::move(Ptr1));
      34             : //     assert(Ptr1 == nullptr);
      35             : //
      36             : //     // Clearing an IntrusiveRefCntPtr decreases the pointee's refcount by 1.
      37             : //     Ptr2.reset();
      38             : //
      39             : //     // The object deletes itself when we return from the function, because
      40             : //     // Ptr3's destructor decrements its refcount to 0.
      41             : //   }
      42             : //
      43             : // You can use IntrusiveRefCntPtr with isa<T>(), dyn_cast<T>(), etc.:
      44             : //
      45             : //   IntrusiveRefCntPtr<MyClass> Ptr(new MyClass());
      46             : //   OtherClass *Other = dyn_cast<OtherClass>(Ptr);  // Ptr.get() not required
      47             : //
      48             : // IntrusiveRefCntPtr works with any class that
      49             : //
      50             : //  - inherits from (ThreadSafe)RefCountedBase,
      51             : //  - has Retain() and Release() methods, or
      52             : //  - specializes IntrusiveRefCntPtrInfo.
      53             : //
      54             : //===----------------------------------------------------------------------===//
      55             : 
      56             : #ifndef LLVM_ADT_INTRUSIVEREFCNTPTR_H
      57             : #define LLVM_ADT_INTRUSIVEREFCNTPTR_H
      58             : 
      59             : #include <atomic>
      60             : #include <cassert>
      61             : #include <cstddef>
      62             : 
      63             : namespace llvm {
      64             : 
      65             : /// A CRTP mixin class that adds reference counting to a type.
      66             : ///
      67             : /// The lifetime of an object which inherits from RefCountedBase is managed by
      68             : /// calls to Release() and Retain(), which increment and decrement the object's
      69             : /// refcount, respectively.  When a Release() call decrements the refcount to 0,
      70             : /// the object deletes itself.
      71             : template <class Derived> class RefCountedBase {
      72             :   mutable unsigned RefCount = 0;
      73             : 
      74             : public:
      75      474040 :   RefCountedBase() = default;
      76        4068 :   RefCountedBase(const RefCountedBase &) {}
      77             : 
      78      621766 :   void Retain() const { ++RefCount; }
      79             : 
      80      572155 :   void Release() const {
      81             :     assert(RefCount > 0 && "Reference count is already zero.");
      82      610188 :     if (--RefCount == 0)
      83      331805 :       delete static_cast<const Derived *>(this);
      84      572155 :   }
      85             : };
      86             : 
      87             : /// A thread-safe version of \c RefCountedBase.
      88             : template <class Derived> class ThreadSafeRefCountedBase {
      89             :   mutable std::atomic<int> RefCount;
      90             : 
      91             : protected:
      92      881400 :   ThreadSafeRefCountedBase() : RefCount(0) {}
      93             : 
      94             : public:
      95     4448280 :   void Retain() const { RefCount.fetch_add(1, std::memory_order_relaxed); }
      96             : 
      97     2219540 :   void Release() const {
      98     4439080 :     int NewRefCount = RefCount.fetch_sub(1, std::memory_order_acq_rel) - 1;
      99             :     assert(NewRefCount >= 0 && "Reference count was already zero.");
     100     2219540 :     if (NewRefCount == 0)
     101      436688 :       delete static_cast<const Derived *>(this);
     102     2219540 :   }
     103             : };
     104             : 
     105             : /// Class you can specialize to provide custom retain/release functionality for
     106             : /// a type.
     107             : ///
     108             : /// Usually specializing this class is not necessary, as IntrusiveRefCntPtr
     109             : /// works with any type which defines Retain() and Release() functions -- you
     110             : /// can define those functions yourself if RefCountedBase doesn't work for you.
     111             : ///
     112             : /// One case when you might want to specialize this type is if you have
     113             : ///  - Foo.h defines type Foo and includes Bar.h, and
     114             : ///  - Bar.h uses IntrusiveRefCntPtr<Foo> in inline functions.
     115             : ///
     116             : /// Because Foo.h includes Bar.h, Bar.h can't include Foo.h in order to pull in
     117             : /// the declaration of Foo.  Without the declaration of Foo, normally Bar.h
     118             : /// wouldn't be able to use IntrusiveRefCntPtr<Foo>, which wants to call
     119             : /// T::Retain and T::Release.
     120             : ///
     121             : /// To resolve this, Bar.h could include a third header, FooFwd.h, which
     122             : /// forward-declares Foo and specializes IntrusiveRefCntPtrInfo<Foo>.  Then
     123             : /// Bar.h could use IntrusiveRefCntPtr<Foo>, although it still couldn't call any
     124             : /// functions on Foo itself, because Foo would be an incomplete type.
     125             : template <typename T> struct IntrusiveRefCntPtrInfo {
     126     8765091 :   static void retain(T *obj) { obj->Retain(); }
     127     3225290 :   static void release(T *obj) { obj->Release(); }
     128             : };
     129             : 
     130             : /// A smart pointer to a reference-counted object that inherits from
     131             : /// RefCountedBase or ThreadSafeRefCountedBase.
     132             : ///
     133             : /// This class increments its pointee's reference count when it is created, and
     134             : /// decrements its refcount when it's destroyed (or is changed to point to a
     135             : /// different object).
     136             : template <typename T> class IntrusiveRefCntPtr {
     137             :   T *Obj = nullptr;
     138             : 
     139             : public:
     140             :   using element_type = T;
     141             : 
     142      216936 :   explicit IntrusiveRefCntPtr() = default;
     143     6928910 :   IntrusiveRefCntPtr(T *obj) : Obj(obj) { retain(); }
     144    48769680 :   IntrusiveRefCntPtr(const IntrusiveRefCntPtr &S) : Obj(S.Obj) { retain(); }
     145     5551592 :   IntrusiveRefCntPtr(IntrusiveRefCntPtr &&S) : Obj(S.Obj) { S.Obj = nullptr; }
     146             : 
     147             :   template <class X>
     148          62 :   IntrusiveRefCntPtr(IntrusiveRefCntPtr<X> &&S) : Obj(S.get()) {
     149          39 :     S.Obj = nullptr;
     150             :   }
     151             : 
     152             :   template <class X>
     153       42722 :   IntrusiveRefCntPtr(const IntrusiveRefCntPtr<X> &S) : Obj(S.get()) {
     154       38660 :     retain();
     155             :   }
     156             : 
     157    33722052 :   ~IntrusiveRefCntPtr() { release(); }
     158             : 
     159             :   IntrusiveRefCntPtr &operator=(IntrusiveRefCntPtr S) {
     160     5418928 :     swap(S);
     161             :     return *this;
     162             :   }
     163             : 
     164     4222455 :   T &operator*() const { return *Obj; }
     165    36605077 :   T *operator->() const { return Obj; }
     166    40628381 :   T *get() const { return Obj; }
     167     2582576 :   explicit operator bool() const { return Obj; }
     168             : 
     169             :   void swap(IntrusiveRefCntPtr &other) {
     170     5418928 :     T *tmp = other.Obj;
     171     5376956 :     other.Obj = Obj;
     172     5418928 :     Obj = tmp;
     173             :   }
     174             : 
     175             :   void reset() {
     176        8223 :     release();
     177        8223 :     Obj = nullptr;
     178             :   }
     179             : 
     180        1025 :   void resetWithoutRelease() { Obj = nullptr; }
     181             : 
     182             : private:
     183             :   void retain() {
     184    25644757 :     if (Obj)
     185    26976965 :       IntrusiveRefCntPtrInfo<T>::retain(Obj);
     186             :   }
     187             : 
     188     6254178 :   void release() {
     189    30373220 :     if (Obj)
     190    24940801 :       IntrusiveRefCntPtrInfo<T>::release(Obj);
     191     6254178 :   }
     192             : 
     193             :   template <typename X> friend class IntrusiveRefCntPtr;
     194             : };
     195             : 
     196             : template <class T, class U>
     197             : inline bool operator==(const IntrusiveRefCntPtr<T> &A,
     198             :                        const IntrusiveRefCntPtr<U> &B) {
     199     1515116 :   return A.get() == B.get();
     200             : }
     201             : 
     202             : template <class T, class U>
     203             : inline bool operator!=(const IntrusiveRefCntPtr<T> &A,
     204             :                        const IntrusiveRefCntPtr<U> &B) {
     205      251660 :   return A.get() != B.get();
     206             : }
     207             : 
     208             : template <class T, class U>
     209             : inline bool operator==(const IntrusiveRefCntPtr<T> &A, U *B) {
     210             :   return A.get() == B;
     211             : }
     212             : 
     213             : template <class T, class U>
     214             : inline bool operator!=(const IntrusiveRefCntPtr<T> &A, U *B) {
     215             :   return A.get() != B;
     216             : }
     217             : 
     218             : template <class T, class U>
     219             : inline bool operator==(T *A, const IntrusiveRefCntPtr<U> &B) {
     220             :   return A == B.get();
     221             : }
     222             : 
     223             : template <class T, class U>
     224             : inline bool operator!=(T *A, const IntrusiveRefCntPtr<U> &B) {
     225             :   return A != B.get();
     226             : }
     227             : 
     228             : template <class T>
     229             : bool operator==(std::nullptr_t A, const IntrusiveRefCntPtr<T> &B) {
     230      150677 :   return !B;
     231             : }
     232             : 
     233             : template <class T>
     234             : bool operator==(const IntrusiveRefCntPtr<T> &A, std::nullptr_t B) {
     235      301354 :   return B == A;
     236             : }
     237             : 
     238             : template <class T>
     239             : bool operator!=(std::nullptr_t A, const IntrusiveRefCntPtr<T> &B) {
     240             :   return !(A == B);
     241             : }
     242             : 
     243             : template <class T>
     244             : bool operator!=(const IntrusiveRefCntPtr<T> &A, std::nullptr_t B) {
     245      301354 :   return !(A == B);
     246             : }
     247             : 
     248             : // Make IntrusiveRefCntPtr work with dyn_cast, isa, and the other idioms from
     249             : // Casting.h.
     250             : template <typename From> struct simplify_type;
     251             : 
     252             : template <class T> struct simplify_type<IntrusiveRefCntPtr<T>> {
     253             :   using SimpleType = T *;
     254             : 
     255             :   static SimpleType getSimplifiedValue(IntrusiveRefCntPtr<T> &Val) {
     256          25 :     return Val.get();
     257             :   }
     258             : };
     259             : 
     260             : template <class T> struct simplify_type<const IntrusiveRefCntPtr<T>> {
     261             :   using SimpleType = /*const*/ T *;
     262             : 
     263             :   static SimpleType getSimplifiedValue(const IntrusiveRefCntPtr<T> &Val) {
     264          21 :     return Val.get();
     265             :   }
     266             : };
     267             : 
     268             : } // end namespace llvm
     269             : 
     270             : #endif // LLVM_ADT_INTRUSIVEREFCNTPTR_H

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