IntrusiveRefCntPtr.h File Reference

This file defines the RefCountedBase, ThreadSafeRefCountedBase, and IntrusiveRefCntPtr classes. More...

#include <atomic>
#include <cassert>
#include <cstddef>
#include <memory>

Go to the source code of this file.

Classes
class	llvm::RefCountedBase< Derived >
	A CRTP mixin class that adds reference counting to a type. More...
class	llvm::ThreadSafeRefCountedBase< Derived >
	A thread-safe version of RefCountedBase. More...
struct	llvm::IntrusiveRefCntPtrInfo< T >
	Class you can specialize to provide custom retain/release functionality for a type. More...
class	llvm::IntrusiveRefCntPtr< T >
	A smart pointer to a reference-counted object that inherits from RefCountedBase or ThreadSafeRefCountedBase. More...
struct	llvm::simplify_type< IntrusiveRefCntPtr< T > >
struct	llvm::simplify_type< const IntrusiveRefCntPtr< T > >

Namespaces
namespace	llvm
	This is an optimization pass for GlobalISel generic memory operations.

Functions
template<class T , class U >
bool	llvm::operator== (const IntrusiveRefCntPtr< T > &A, const IntrusiveRefCntPtr< U > &B)
template<class T , class U >
bool	llvm::operator!= (const IntrusiveRefCntPtr< T > &A, const IntrusiveRefCntPtr< U > &B)
template<class T , class U >
bool	llvm::operator== (const IntrusiveRefCntPtr< T > &A, U *B)
template<class T , class U >
bool	llvm::operator!= (const IntrusiveRefCntPtr< T > &A, U *B)
template<class T , class U >
bool	llvm::operator== (T *A, const IntrusiveRefCntPtr< U > &B)
template<class T , class U >
bool	llvm::operator!= (T *A, const IntrusiveRefCntPtr< U > &B)
template<class T >
bool	llvm::operator== (std::nullptr_t, const IntrusiveRefCntPtr< T > &B)
template<class T >
bool	llvm::operator== (const IntrusiveRefCntPtr< T > &A, std::nullptr_t B)
template<class T >
bool	llvm::operator!= (std::nullptr_t A, const IntrusiveRefCntPtr< T > &B)
template<class T >
bool	llvm::operator!= (const IntrusiveRefCntPtr< T > &A, std::nullptr_t B)
template<typename T , typename... Args>
IntrusiveRefCntPtr< T >	llvm::makeIntrusiveRefCnt (Args &&...A)
	Factory function for creating intrusive ref counted pointers.

Detailed Description

This file defines the RefCountedBase, ThreadSafeRefCountedBase, and IntrusiveRefCntPtr classes.

IntrusiveRefCntPtr is a smart pointer to an object which maintains a reference count. (ThreadSafe)RefCountedBase is a mixin class that adds a refcount member variable and methods for updating the refcount. An object that inherits from (ThreadSafe)RefCountedBase deletes itself when its refcount hits zero.

For example:

class MyClass : public RefCountedBase<MyClass> {};
 
void foo() {
  // Constructing an IntrusiveRefCntPtr increases the pointee's refcount
  // by 1 (from 0 in this case).
  IntrusiveRefCntPtr<MyClass> Ptr1(new MyClass());
 
  // Copying an IntrusiveRefCntPtr increases the pointee's refcount by 1.
  IntrusiveRefCntPtr<MyClass> Ptr2(Ptr1);
 
  // Constructing an IntrusiveRefCntPtr has no effect on the object's
  // refcount.  After a move, the moved-from pointer is null.
  IntrusiveRefCntPtr<MyClass> Ptr3(std::move(Ptr1));
  assert(Ptr1 == nullptr);
 
  // Clearing an IntrusiveRefCntPtr decreases the pointee's refcount by 1.
  Ptr2.reset();
 
  // The object deletes itself when we return from the function, because
  // Ptr3's destructor decrements its refcount to 0.
}

You can use IntrusiveRefCntPtr with isa<T>(), dyn_cast<T>(), etc.:

IntrusiveRefCntPtr<MyClass> Ptr(new MyClass());
OtherClass *Other = dyn_cast<OtherClass>(Ptr);  // Ptr.get() not required

IntrusiveRefCntPtr works with any class that

• inherits from (ThreadSafe)RefCountedBase,
• has Retain() and Release() methods, or
• specializes IntrusiveRefCntPtrInfo.

Definition in file IntrusiveRefCntPtr.h.