[libcxx-commits] [libcxx] [libc++] Optimize the two range overload of mismatch (PR #86853)

[Louis Dionne via libcxx-commits]

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@@ -107,17 +108,42 @@ mismatch(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __fi
 }
 
 #if _LIBCPP_STD_VER >= 14
+template <class _Iter1, class _Sent1, class _Iter2, class _Sent2, class _Pred, class _Proj1, class _Proj2>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_Iter1, _Iter2> __mismatch(
+    _Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2, _Pred& __pred, _Proj1& __proj1, _Proj2& __proj2) {
+  while (__first1 != __last1 && __first2 != __last2) {
+    if (!std::__invoke(__pred, std::__invoke(__proj1, *__first1), std::__invoke(__proj2, *__first2)))
+      break;
+    ++__first1;
+    ++__first2;
+  }
+  return {std::move(__first1), std::move(__first2)};
+}
+
+template <class _Tp, class _Pred, class _Proj1, class _Proj2>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_Tp*, _Tp*>
+__mismatch(_Tp* __first1, _Tp* __last1, _Tp* __first2, _Tp* __last2, _Pred& __pred, _Proj1 __proj1, _Proj2 __proj2) {
+  auto __len = std::min(__last1 - __first1, __last2 - __first2);
+  return std::__mismatch(__first1, __first1 + __len, __first2, __pred, __proj1, __proj2);
+}
+
 template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
----------------
ldionne wrote:

Can you just confirm that our existing tests for constexpr have proper coverage to avoid breaking that?

https://github.com/llvm/llvm-project/pull/86853