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289 lines
8.5 KiB
C++
289 lines
8.5 KiB
C++
//== llvm/ADT/IntrusiveRefCntPtr.h - Smart Refcounting Pointer ---*- C++ -*-==//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines IntrusiveRefCntPtr, a template class that
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// implements a "smart" pointer for objects that maintain their own
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// internal reference count, and RefCountedBase/RefCountedBaseVPTR, two
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// generic base classes for objects that wish to have their lifetimes
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// managed using reference counting.
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//
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// IntrusiveRefCntPtr is similar to Boost's intrusive_ptr with added
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// LLVM-style casting.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_INTRUSIVEREFCNTPTR_H
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#define LLVM_ADT_INTRUSIVEREFCNTPTR_H
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#include <atomic>
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#include <cassert>
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#include <cstddef>
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namespace llvm {
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template <class T>
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class IntrusiveRefCntPtr;
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//===----------------------------------------------------------------------===//
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/// RefCountedBase - A generic base class for objects that wish to
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/// have their lifetimes managed using reference counts. Classes
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/// subclass RefCountedBase to obtain such functionality, and are
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/// typically handled with IntrusiveRefCntPtr "smart pointers" (see below)
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/// which automatically handle the management of reference counts.
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/// Objects that subclass RefCountedBase should not be allocated on
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/// the stack, as invoking "delete" (which is called when the
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/// reference count hits 0) on such objects is an error.
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//===----------------------------------------------------------------------===//
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template <class Derived>
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class RefCountedBase {
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mutable unsigned ref_cnt;
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public:
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RefCountedBase() : ref_cnt(0) {}
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RefCountedBase(const RefCountedBase &) : ref_cnt(0) {}
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void Retain() const { ++ref_cnt; }
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void Release() const {
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assert (ref_cnt > 0 && "Reference count is already zero.");
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if (--ref_cnt == 0) delete static_cast<const Derived*>(this);
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}
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};
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//===----------------------------------------------------------------------===//
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/// RefCountedBaseVPTR - A class that has the same function as
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/// RefCountedBase, but with a virtual destructor. Should be used
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/// instead of RefCountedBase for classes that already have virtual
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/// methods to enforce dynamic allocation via 'new'. Classes that
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/// inherit from RefCountedBaseVPTR can't be allocated on stack -
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/// attempting to do this will produce a compile error.
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//===----------------------------------------------------------------------===//
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class RefCountedBaseVPTR {
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mutable unsigned ref_cnt;
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virtual void anchor();
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protected:
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RefCountedBaseVPTR() : ref_cnt(0) {}
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RefCountedBaseVPTR(const RefCountedBaseVPTR &) : ref_cnt(0) {}
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virtual ~RefCountedBaseVPTR() {}
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void Retain() const { ++ref_cnt; }
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void Release() const {
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assert (ref_cnt > 0 && "Reference count is already zero.");
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if (--ref_cnt == 0) delete this;
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}
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template <typename T>
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friend struct IntrusiveRefCntPtrInfo;
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};
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template <typename T> struct IntrusiveRefCntPtrInfo {
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static void retain(T *obj) { obj->Retain(); }
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static void release(T *obj) { obj->Release(); }
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};
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/// \brief A thread-safe version of \c llvm::RefCountedBase.
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///
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/// A generic base class for objects that wish to have their lifetimes managed
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/// using reference counts. Classes subclass \c ThreadSafeRefCountedBase to
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/// obtain such functionality, and are typically handled with
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/// \c IntrusiveRefCntPtr "smart pointers" which automatically handle the
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/// management of reference counts.
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template <class Derived>
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class ThreadSafeRefCountedBase {
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mutable std::atomic<int> RefCount;
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protected:
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ThreadSafeRefCountedBase() : RefCount(0) {}
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public:
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void Retain() const { ++RefCount; }
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void Release() const {
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int NewRefCount = --RefCount;
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assert(NewRefCount >= 0 && "Reference count was already zero.");
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if (NewRefCount == 0)
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delete static_cast<const Derived*>(this);
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}
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};
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//===----------------------------------------------------------------------===//
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/// IntrusiveRefCntPtr - A template class that implements a "smart pointer"
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/// that assumes the wrapped object has a reference count associated
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/// with it that can be managed via calls to
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/// IntrusivePtrAddRef/IntrusivePtrRelease. The smart pointers
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/// manage reference counts via the RAII idiom: upon creation of
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/// smart pointer the reference count of the wrapped object is
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/// incremented and upon destruction of the smart pointer the
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/// reference count is decremented. This class also safely handles
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/// wrapping NULL pointers.
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///
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/// Reference counting is implemented via calls to
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/// Obj->Retain()/Obj->Release(). Release() is required to destroy
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/// the object when the reference count reaches zero. Inheriting from
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/// RefCountedBase/RefCountedBaseVPTR takes care of this
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/// automatically.
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//===----------------------------------------------------------------------===//
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template <typename T>
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class IntrusiveRefCntPtr {
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T* Obj;
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public:
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typedef T element_type;
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explicit IntrusiveRefCntPtr() : Obj(nullptr) {}
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IntrusiveRefCntPtr(T* obj) : Obj(obj) {
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retain();
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}
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IntrusiveRefCntPtr(const IntrusiveRefCntPtr& S) : Obj(S.Obj) {
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retain();
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}
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IntrusiveRefCntPtr(IntrusiveRefCntPtr&& S) : Obj(S.Obj) {
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S.Obj = nullptr;
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}
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template <class X>
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IntrusiveRefCntPtr(IntrusiveRefCntPtr<X>&& S) : Obj(S.get()) {
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S.Obj = 0;
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}
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template <class X>
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IntrusiveRefCntPtr(const IntrusiveRefCntPtr<X>& S)
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: Obj(S.get()) {
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retain();
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}
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IntrusiveRefCntPtr& operator=(IntrusiveRefCntPtr S) {
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swap(S);
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return *this;
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}
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~IntrusiveRefCntPtr() { release(); }
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T& operator*() const { return *Obj; }
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T* operator->() const { return Obj; }
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T* get() const { return Obj; }
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explicit operator bool() const { return Obj; }
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void swap(IntrusiveRefCntPtr& other) {
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T* tmp = other.Obj;
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other.Obj = Obj;
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Obj = tmp;
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}
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void reset() {
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release();
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Obj = nullptr;
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}
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void resetWithoutRelease() {
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Obj = 0;
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}
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private:
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void retain() { if (Obj) IntrusiveRefCntPtrInfo<T>::retain(Obj); }
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void release() { if (Obj) IntrusiveRefCntPtrInfo<T>::release(Obj); }
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template <typename X>
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friend class IntrusiveRefCntPtr;
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};
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template<class T, class U>
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inline bool operator==(const IntrusiveRefCntPtr<T>& A,
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const IntrusiveRefCntPtr<U>& B)
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{
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return A.get() == B.get();
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}
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template<class T, class U>
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inline bool operator!=(const IntrusiveRefCntPtr<T>& A,
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const IntrusiveRefCntPtr<U>& B)
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{
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return A.get() != B.get();
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}
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template<class T, class U>
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inline bool operator==(const IntrusiveRefCntPtr<T>& A,
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U* B)
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{
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return A.get() == B;
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}
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template<class T, class U>
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inline bool operator!=(const IntrusiveRefCntPtr<T>& A,
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U* B)
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{
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return A.get() != B;
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}
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template<class T, class U>
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inline bool operator==(T* A,
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const IntrusiveRefCntPtr<U>& B)
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{
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return A == B.get();
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}
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template<class T, class U>
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inline bool operator!=(T* A,
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const IntrusiveRefCntPtr<U>& B)
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{
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return A != B.get();
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}
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template <class T>
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bool operator==(std::nullptr_t A, const IntrusiveRefCntPtr<T> &B) {
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return !B;
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}
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template <class T>
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bool operator==(const IntrusiveRefCntPtr<T> &A, std::nullptr_t B) {
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return B == A;
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}
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template <class T>
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bool operator!=(std::nullptr_t A, const IntrusiveRefCntPtr<T> &B) {
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return !(A == B);
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}
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template <class T>
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bool operator!=(const IntrusiveRefCntPtr<T> &A, std::nullptr_t B) {
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return !(A == B);
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}
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//===----------------------------------------------------------------------===//
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// LLVM-style downcasting support for IntrusiveRefCntPtr objects
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//===----------------------------------------------------------------------===//
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template <typename From> struct simplify_type;
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template<class T> struct simplify_type<IntrusiveRefCntPtr<T> > {
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typedef T* SimpleType;
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static SimpleType getSimplifiedValue(IntrusiveRefCntPtr<T>& Val) {
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return Val.get();
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}
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};
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template<class T> struct simplify_type<const IntrusiveRefCntPtr<T> > {
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typedef /*const*/ T* SimpleType;
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static SimpleType getSimplifiedValue(const IntrusiveRefCntPtr<T>& Val) {
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return Val.get();
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}
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};
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} // end namespace llvm
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#endif // LLVM_ADT_INTRUSIVEREFCNTPTR_H
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