diff --git a/include/llvm/System/Atomic.h b/include/llvm/System/Atomic.h
index c4049d4..a94ad2d 100644
--- a/include/llvm/System/Atomic.h
+++ b/include/llvm/System/Atomic.h
@@ -20,13 +20,14 @@
   namespace sys {
     void MemoryFence();
 
-    typedef uint32_t cas_flag;
-    cas_flag CompareAndSwap(volatile cas_flag* ptr,
-                            cas_flag new_value,
-                            cas_flag old_value);
-    cas_flag AtomicIncrement(volatile cas_flag* ptr);
-    cas_flag AtomicDecrement(volatile cas_flag* ptr);
-    cas_flag AtomicAdd(volatile cas_flag* ptr, cas_flag val);
+    uint32_t CompareAndSwap32(volatile uint32_t* ptr,
+                            uint32_t new_value,
+                            uint32_t old_value);
+    uint32_t AtomicIncrement32(volatile uint32_t* ptr);
+    uint32_t AtomicDecrement32(volatile uint32_t* ptr);
+    uint32_t AtomicAdd32(volatile uint32_t* ptr, uint32_t val);
+    
+    uint64_t AtomicAdd64(volatile uint64_t* ptr, uint64_t val);
   }
 }
 
diff --git a/include/llvm/Type.h b/include/llvm/Type.h
index d439233..8c07b3e 100644
--- a/include/llvm/Type.h
+++ b/include/llvm/Type.h
@@ -103,7 +103,7 @@
   /// has no AbstractTypeUsers, the type is deleted.  This is only sensical for
   /// derived types.
   ///
-  mutable sys::cas_flag RefCount;
+  mutable uint32_t RefCount;
 
   const Type *getForwardedTypeInternal() const;
 
@@ -338,7 +338,7 @@
 
   void addRef() const {
     assert(isAbstract() && "Cannot add a reference to a non-abstract type!");
-    sys::AtomicIncrement(&RefCount);
+    sys::AtomicIncrement32(&RefCount);
   }
 
   void dropRef() const {
@@ -347,8 +347,8 @@
 
     // If this is the last PATypeHolder using this object, and there are no
     // PATypeHandles using it, the type is dead, delete it now.
-    sys::cas_flag OldCount = sys::AtomicDecrement(&RefCount);
-    if (OldCount == 0 && AbstractTypeUsers.empty())
+    uint32_t Count = sys::AtomicDecrement32(&RefCount);
+    if (Count == 0 && AbstractTypeUsers.empty())
       this->destroy();
   }
   
diff --git a/lib/System/Atomic.cpp b/lib/System/Atomic.cpp
index 6e751a3..65e1469 100644
--- a/lib/System/Atomic.cpp
+++ b/lib/System/Atomic.cpp
@@ -35,11 +35,11 @@
 #endif
 }
 
-sys::cas_flag sys::CompareAndSwap(volatile sys::cas_flag* ptr,
-                                  sys::cas_flag new_value,
-                                  sys::cas_flag old_value) {
+uint32_t sys::CompareAndSwap32(volatile uint32_t* ptr,
+                               uint32_t new_value,
+                               uint32_t old_value) {
 #if LLVM_MULTITHREADED==0
-  sys::cas_flag result = *ptr;
+  uint32_t result = *ptr;
   if (result == old_value)
     *ptr = new_value;
   return result;
@@ -52,7 +52,7 @@
 #endif
 }
 
-sys::cas_flag sys::AtomicIncrement(volatile sys::cas_flag* ptr) {
+uint32_t sys::AtomicIncrement32(volatile uint32_t* ptr) {
 #if LLVM_MULTITHREADED==0
   ++(*ptr);
   return *ptr;
@@ -65,7 +65,7 @@
 #endif
 }
 
-sys::cas_flag sys::AtomicDecrement(volatile sys::cas_flag* ptr) {
+uint32_t sys::AtomicDecrement32(volatile uint32_t* ptr) {
 #if LLVM_MULTITHREADED==0
   --(*ptr);
   return *ptr;
@@ -78,7 +78,7 @@
 #endif
 }
 
-sys::cas_flag sys::AtomicAdd(volatile sys::cas_flag* ptr, sys::cas_flag val) {
+uint32_t sys::AtomicAdd32(volatile uint32_t* ptr, uint32_t val) {
 #if LLVM_MULTITHREADED==0
   *ptr += val;
   return *ptr;
@@ -91,4 +91,16 @@
 #endif
 }
 
+uint64_t sys::AtomicAdd64(volatile uint64_t* ptr, uint64_t val) {
+#if LLVM_MULTITHREADED==0
+  *ptr += val;
+  return *ptr;
+#elif defined(__GNUC__)
+  return __sync_add_and_fetch(ptr, val);
+#elif defined(_MSC_VER)
+  return InterlockedAdd64(ptr, val);
+#else
+#  error No atomic add implementation for your platform!
+#endif
+}
 
diff --git a/lib/VMCore/Mangler.cpp b/lib/VMCore/Mangler.cpp
index 1a68b89..0f6f216 100644
--- a/lib/VMCore/Mangler.cpp
+++ b/lib/VMCore/Mangler.cpp
@@ -168,7 +168,7 @@
     static uint32_t GlobalID = 0;
     
     unsigned OldID = GlobalID;
-    sys::AtomicIncrement(&GlobalID);
+    sys::AtomicIncrement32(&GlobalID);
     
     Name = "__unnamed_" + utostr(TypeUniqueID) + "_" + utostr(OldID);
   } else {