1 files changed, 62 insertions, 21 deletions

diff --git a/include/llvm/ADT/IntrusiveRefCntPtr.h b/include/llvm/ADT/IntrusiveRefCntPtr.h
index b8b88619957e..f9df3781257e 100644
--- a/include/llvm/ADT/IntrusiveRefCntPtr.h
+++ b/include/llvm/ADT/IntrusiveRefCntPtr.h
@@ -23,6 +23,7 @@
 
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Compiler.h"
+#include <atomic>
 #include <memory>
 
 namespace llvm {
@@ -88,6 +89,31 @@ namespace llvm {
     static void retain(T *obj) { obj->Retain(); }
     static void release(T *obj) { obj->Release(); }
   };
+
+/// \brief A thread-safe version of \c llvm::RefCountedBase.
+///
+/// A generic base class for objects that wish to have their lifetimes managed
+/// using reference counts. Classes subclass \c ThreadSafeRefCountedBase to
+/// obtain such functionality, and are typically handled with
+/// \c IntrusiveRefCntPtr "smart pointers" which automatically handle the
+/// management of reference counts.
+template <class Derived>
+class ThreadSafeRefCountedBase {
+  mutable std::atomic<int> RefCount;
+
+protected:
+  ThreadSafeRefCountedBase() : RefCount(0) {}
+
+public:
+  void Retain() const { ++RefCount; }
+
+  void Release() const {
+    int NewRefCount = --RefCount;
+    assert(NewRefCount >= 0 && "Reference count was already zero.");
+    if (NewRefCount == 0)
+      delete static_cast<const Derived*>(this);
+  }
+};
   
 //===----------------------------------------------------------------------===//
 /// IntrusiveRefCntPtr - A template class that implements a "smart pointer"
@@ -109,11 +135,11 @@ namespace llvm {
   template <typename T>
   class IntrusiveRefCntPtr {
     T* Obj;
-    typedef IntrusiveRefCntPtr this_type;
+
   public:
     typedef T element_type;
 
-    explicit IntrusiveRefCntPtr() : Obj(0) {}
+    explicit IntrusiveRefCntPtr() : Obj(nullptr) {}
 
     IntrusiveRefCntPtr(T* obj) : Obj(obj) {
       retain();
@@ -123,20 +149,18 @@ namespace llvm {
       retain();
     }
 
-#if LLVM_HAS_RVALUE_REFERENCES
     IntrusiveRefCntPtr(IntrusiveRefCntPtr&& S) : Obj(S.Obj) {
-      S.Obj = 0;
+      S.Obj = nullptr;
     }
 
     template <class X>
-    IntrusiveRefCntPtr(IntrusiveRefCntPtr<X>&& S) : Obj(S.getPtr()) {
+    IntrusiveRefCntPtr(IntrusiveRefCntPtr<X>&& S) : Obj(S.get()) {
       S.Obj = 0;
     }
-#endif
 
     template <class X>
     IntrusiveRefCntPtr(const IntrusiveRefCntPtr<X>& S)
-      : Obj(S.getPtr()) {
+      : Obj(S.get()) {
       retain();
     }
 
@@ -151,12 +175,9 @@ namespace llvm {
 
     T* operator->() const { return Obj; }
 
-    T* getPtr() const { return Obj; }
+    T* get() const { return Obj; }
 
-    typedef T* (IntrusiveRefCntPtr::*unspecified_bool_type) () const;
-    operator unspecified_bool_type() const {
-      return Obj == 0 ? 0 : &IntrusiveRefCntPtr::getPtr;
-    }
+    LLVM_EXPLICIT operator bool() const { return Obj; }
 
     void swap(IntrusiveRefCntPtr& other) {
       T* tmp = other.Obj;
@@ -166,7 +187,7 @@ namespace llvm {
 
     void reset() {
       release();
-      Obj = 0;
+      Obj = nullptr;
     }
 
     void resetWithoutRelease() {
@@ -182,42 +203,62 @@ namespace llvm {
   inline bool operator==(const IntrusiveRefCntPtr<T>& A,
                          const IntrusiveRefCntPtr<U>& B)
   {
-    return A.getPtr() == B.getPtr();
+    return A.get() == B.get();
   }
 
   template<class T, class U>
   inline bool operator!=(const IntrusiveRefCntPtr<T>& A,
                          const IntrusiveRefCntPtr<U>& B)
   {
-    return A.getPtr() != B.getPtr();
+    return A.get() != B.get();
   }
 
   template<class T, class U>
   inline bool operator==(const IntrusiveRefCntPtr<T>& A,
                          U* B)
   {
-    return A.getPtr() == B;
+    return A.get() == B;
   }
 
   template<class T, class U>
   inline bool operator!=(const IntrusiveRefCntPtr<T>& A,
                          U* B)
   {
-    return A.getPtr() != B;
+    return A.get() != B;
   }
 
   template<class T, class U>
   inline bool operator==(T* A,
                          const IntrusiveRefCntPtr<U>& B)
   {
-    return A == B.getPtr();
+    return A == B.get();
   }
 
   template<class T, class U>
   inline bool operator!=(T* A,
                          const IntrusiveRefCntPtr<U>& B)
   {
-    return A != B.getPtr();
+    return A != B.get();
+  }
+
+  template <class T>
+  bool operator==(std::nullptr_t A, const IntrusiveRefCntPtr<T> &B) {
+    return !B;
+  }
+
+  template <class T>
+  bool operator==(const IntrusiveRefCntPtr<T> &A, std::nullptr_t B) {
+    return B == A;
+  }
+
+  template <class T>
+  bool operator!=(std::nullptr_t A, const IntrusiveRefCntPtr<T> &B) {
+    return !(A == B);
+  }
+
+  template <class T>
+  bool operator!=(const IntrusiveRefCntPtr<T> &A, std::nullptr_t B) {
+    return !(A == B);
   }
 
 //===----------------------------------------------------------------------===//
@@ -227,14 +268,14 @@ namespace llvm {
   template<class T> struct simplify_type<IntrusiveRefCntPtr<T> > {
     typedef T* SimpleType;
     static SimpleType getSimplifiedValue(IntrusiveRefCntPtr<T>& Val) {
-      return Val.getPtr();
+      return Val.get();
     }
   };
 
   template<class T> struct simplify_type<const IntrusiveRefCntPtr<T> > {
     typedef /*const*/ T* SimpleType;
     static SimpleType getSimplifiedValue(const IntrusiveRefCntPtr<T>& Val) {
-      return Val.getPtr();
+      return Val.get();
     }
   };