[libc++] [NFC] Remove an unused parameter from `__sift_down`

[• Quuxplusone]

Summary

Get this NFC change out of the way so it's not distracting me as I think about https://github.com/llvm/llvm-project/issues/10008 :)

[ldionne]

LGTM, but let's ensure we were not exporting an explicit specialization of this one from the dylib (otherwise that would break ABI).

Running check-cxx-abilist or running CI would tell.

libcxx/include/__algorithm/make_heap.h

 {
     typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
     difference_type __n = __last - __first;
     if (__n > 1)
     {
         // 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);
         }
     }
 }
 
 template <class _RandomAccessIterator, class _Compare>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 void
 make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)

libcxx/include/__algorithm/partial_sort.h

 {
     _VSTD::__make_heap<_Compare>(__first, __middle, __comp);
     typename iterator_traits<_RandomAccessIterator>::difference_type __len = __middle - __first;
     for (_RandomAccessIterator __i = __middle; __i != __last; ++__i)
     {
         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);
 }
 
 template <class _RandomAccessIterator, class _Compare>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 void

libcxx/include/__algorithm/partial_sort_copy.h

if (__r != __result_last)
         for (; __first != __last && __r != __result_last; ++__first, (void) ++__r)
             *__r = *__first;
         _VSTD::__make_heap<_Compare>(__result_first, __r, __comp);
         typename iterator_traits<_RandomAccessIterator>::difference_type __len = __r - __result_first;
         for (; __first != __last; ++__first)
             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);
     }
     return __r;
 }
 
 template <class _InputIterator, class _RandomAccessIterator, class _Compare>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17

libcxx/include/__algorithm/pop_heap.h

 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 void
 __pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
            typename iterator_traits<_RandomAccessIterator>::difference_type __len)
 {
     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);
     }
 }
 
 template <class _RandomAccessIterator, class _Compare>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 void
 pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
 {

libcxx/include/__algorithm/sift_down.h

 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 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)
 {
     typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
     typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
     // left-child of __start is at 2 * __start + 1
     // right-child of __start is at 2 * __start + 2
     difference_type __child = __start - __first;
 
     if (__len < 2 || (__len - 2) / 2 < __child)
         return;
 
     __child = 2 * __child + 1;
     _RandomAccessIterator __child_i = __first + __child;
 
     if ((__child + 1) < __len && __comp(*__child_i, *(__child_i + difference_type(1)))) {
         // right-child exists and is greater than left-child
         ++__child_i;
         ++__child;
     }
 
     // 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));
     do
     {
         // we are not in heap-order, swap the parent with its largest child
         *__start = _VSTD::move(*__child_i);
         __start = __child_i;