[libcxx-commits] [libcxx] [libc++] Optimize lexicographical_compare (PR #65279)

[Louis Dionne via libcxx-commits]

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@@ -34,23 +36,24 @@ namespace ranges {
 namespace __lexicographical_compare {
 struct __fn {
   template <class _Iter1, class _Sent1, class _Iter2, class _Sent2, class _Proj1, class _Proj2, class _Comp>
-  _LIBCPP_HIDE_FROM_ABI constexpr static bool __lexicographical_compare_impl(
+  static _LIBCPP_HIDE_FROM_ABI constexpr bool __lexicographical_compare_unwrap(
       _Iter1 __first1,
       _Sent1 __last1,
       _Iter2 __first2,
       _Sent2 __last2,
       _Comp& __comp,
       _Proj1& __proj1,
       _Proj2& __proj2) {
-    while (__first2 != __last2) {
-      if (__first1 == __last1 || std::invoke(__comp, std::invoke(__proj1, *__first1), std::invoke(__proj2, *__first2)))
-        return true;
-      if (std::invoke(__comp, std::invoke(__proj2, *__first2), std::invoke(__proj1, *__first1)))
-        return false;
-      ++__first1;
-      ++__first2;
-    }
-    return false;
+    auto [__first1_un, __last1_un] = std::__unwrap_range(std::move(__first1), std::move(__last1));
+    auto [__first2_un, __last2_un] = std::__unwrap_range(std::move(__first2), std::move(__last2));
+    return std::__lexicographical_compare(
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ldionne wrote:

Don't you need to pass through the `AlgPolicy`? Specifically, you will be calling `std::mismatch` (not `ranges::mismatch`) from here under the hood. Is that fine?

Answer: No, `__mismatch` doesn't accept an algorithm policy.

https://github.com/llvm/llvm-project/pull/65279