vector::emplace_back was mistakenly requiring move assignable. Fixed that and...

vector::emplace_back was mistakenly requiring move assignable.  Fixed that and did a little drive-by optimization at the same time.  This fixes http://llvm.org/bugs/show_bug.cgi?id=12085.

llvm-svn: 151492

libcxx/include/vector

@@ -796,6 +796,11 @@ private:
 #else
         __push_back_slow_path(_Up& __x);
 #endif
+#if !defined(_LIBCPP_HAS_NO_VARIADICS) && !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+    template <class... _Args>
+        void
+        __emplace_back_slow_path(_Args&&... __args);
+#endif
 };
 
 template <class _Tp, class _Allocator>
@@ -1495,6 +1500,19 @@ vector<_Tp, _Allocator>::push_back(value_type&& __x)
 template <class _Tp, class _Allocator>
 template <class... _Args>
 void
+vector<_Tp, _Allocator>::__emplace_back_slow_path(_Args&&... __args)
+{
+    allocator_type& __a = this->__alloc();
+    __split_buffer<value_type, allocator_type&> __v(__recommend(size() + 1), size(), __a);
+//    __v.emplace_back(_VSTD::forward<_Args>(__args)...);
+    __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(__v.__end_++), _VSTD::forward<_Args>(__args)...);
+    __swap_out_circular_buffer(__v);
+}
+
+template <class _Tp, class _Allocator>
+template <class... _Args>
+_LIBCPP_INLINE_VISIBILITY inline
+void
 vector<_Tp, _Allocator>::emplace_back(_Args&&... __args)
 {
     if (this->__end_ < this->__end_cap())
@@ -1505,12 +1523,7 @@ vector<_Tp, _Allocator>::emplace_back(_Args&&... __args)
         ++this->__end_;
     }
     else
-    {
-        allocator_type& __a = this->__alloc();
-        __split_buffer<value_type, allocator_type&> __v(__recommend(size() + 1), size(), __a);
-        __v.emplace_back(_VSTD::forward<_Args>(__args)...);
-        __swap_out_circular_buffer(__v);
-    }
+        __emplace_back_slow_path(_VSTD::forward<_Args>(__args)...);
 }
 
 #endif  // _LIBCPP_HAS_NO_VARIADICS