[libcxx-commits] [libcxx] [libc++] Optimize std::min_element (PR #100616)

[Louis Dionne via libcxx-commits]

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@@ -27,20 +28,115 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+template <class _Iter, class _Sent, class = void>
+struct __ConstTimeDistance : false_type {};
+
+#if _LIBCPP_STD_VER >= 20
+
+template <class _Iter, class _Sent>
+struct __ConstTimeDistance< _Iter, _Sent, __enable_if_t< sized_sentinel_for<_Sent, _Iter> >> : true_type {};
+
+#else
+
+template <class _Iter>
+struct __ConstTimeDistance<
+    _Iter,
+    _Iter,
+    __enable_if_t< is_same<typename iterator_traits<_Iter>::iterator_category, random_access_iterator_tag>::value> >
+    : true_type {};
+
+#endif // _LIBCPP_STD_VER >= 20
+
 template <class _Comp, class _Iter, class _Sent, class _Proj>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Iter
-__min_element(_Iter __first, _Sent __last, _Comp& __comp, _Proj& __proj) {
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Iter __min_element(
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ldionne wrote:

Let's use `__enable_if_t` instead of using `true_type` and `false_type` overloads.

https://github.com/llvm/llvm-project/pull/100616