diff --git a/libcxx/include/__algorithm/make_heap.h b/libcxx/include/__algorithm/make_heap.h
--- a/libcxx/include/__algorithm/make_heap.h
+++ b/libcxx/include/__algorithm/make_heap.h
@@ -32,7 +32,7 @@
         // start from the first parent, there is no need to consider children
         for (difference_type __start = (__n - 2) / 2; __start >= 0; --__start)
         {
-            _VSTD::__sift_down<_Compare>(__first, __last, __comp, __n, __first + __start);
+            _VSTD::__sift_down<_Compare>(__first, __comp, __n, __first + __start);
         }
     }
 }
diff --git a/libcxx/include/__algorithm/partial_sort.h b/libcxx/include/__algorithm/partial_sort.h
--- a/libcxx/include/__algorithm/partial_sort.h
+++ b/libcxx/include/__algorithm/partial_sort.h
@@ -40,7 +40,7 @@
         if (__comp(*__i, *__first))
         {
             swap(*__i, *__first);
-            _VSTD::__sift_down<_Compare>(__first, __middle, __comp, __len, __first);
+            _VSTD::__sift_down<_Compare>(__first, __comp, __len, __first);
         }
     }
     _VSTD::__sort_heap<_Compare>(__first, __middle, __comp);
diff --git a/libcxx/include/__algorithm/partial_sort_copy.h b/libcxx/include/__algorithm/partial_sort_copy.h
--- a/libcxx/include/__algorithm/partial_sort_copy.h
+++ b/libcxx/include/__algorithm/partial_sort_copy.h
@@ -40,7 +40,7 @@
             if (__comp(*__first, *__result_first))
             {
                 *__result_first = *__first;
-                _VSTD::__sift_down<_Compare>(__result_first, __r, __comp, __len, __result_first);
+                _VSTD::__sift_down<_Compare>(__result_first, __comp, __len, __result_first);
             }
         _VSTD::__sort_heap<_Compare>(__result_first, __r, __comp);
     }
diff --git a/libcxx/include/__algorithm/pop_heap.h b/libcxx/include/__algorithm/pop_heap.h
--- a/libcxx/include/__algorithm/pop_heap.h
+++ b/libcxx/include/__algorithm/pop_heap.h
@@ -31,7 +31,7 @@
     if (__len > 1)
     {
         swap(*__first, *--__last);
-        _VSTD::__sift_down<_Compare>(__first, __last, __comp, __len - 1, __first);
+        _VSTD::__sift_down<_Compare>(__first, __comp, __len - 1, __first);
     }
 }
 
diff --git a/libcxx/include/__algorithm/sift_down.h b/libcxx/include/__algorithm/sift_down.h
--- a/libcxx/include/__algorithm/sift_down.h
+++ b/libcxx/include/__algorithm/sift_down.h
@@ -21,8 +21,7 @@
 
 template <class _Compare, class _RandomAccessIterator>
 _LIBCPP_CONSTEXPR_AFTER_CXX11 void
-__sift_down(_RandomAccessIterator __first, _RandomAccessIterator /*__last*/,
-            _Compare __comp,
+__sift_down(_RandomAccessIterator __first, _Compare __comp,
             typename iterator_traits<_RandomAccessIterator>::difference_type __len,
             _RandomAccessIterator __start)
 {
@@ -46,7 +45,7 @@
 
     // check if we are in heap-order
     if (__comp(*__child_i, *__start))
-        // we are, __start is larger than it's largest child
+        // we are, __start is larger than its largest child
         return;
 
     value_type __top(_VSTD::move(*__start));