1 files changed, 49 insertions, 4 deletions
diff --git a/libcxx/include/__algorithm/find.h b/libcxx/include/__algorithm/find.h
index e51dc9bb160a..e0de5032878e 100644
--- a/libcxx/include/__algorithm/find.h
+++ b/libcxx/include/__algorithm/find.h
@@ -10,7 +10,16 @@
 #ifndef _LIBCPP___ALGORITHM_FIND_H
 #define _LIBCPP___ALGORITHM_FIND_H
 
+#include <__algorithm/unwrap_iter.h>
 #include <__config>
+#include <__functional/identity.h>
+#include <__functional/invoke.h>
+#include <__string/constexpr_c_functions.h>
+#include <__type_traits/is_same.h>
+
+#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+#  include <cwchar>
+#endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -18,15 +27,51 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _InputIterator, class _Tp>
-_LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 _InputIterator
-find(_InputIterator __first, _InputIterator __last, const _Tp& __value) {
+template <class _Iter, class _Sent, class _Tp, class _Proj>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Iter
+__find_impl(_Iter __first, _Sent __last, const _Tp& __value, _Proj& __proj) {
   for (; __first != __last; ++__first)
-    if (*__first == __value)
+    if (std::__invoke(__proj, *__first) == __value)
       break;
   return __first;
 }
 
+template <class _Tp,
+          class _Up,
+          class _Proj,
+          __enable_if_t<__is_identity<_Proj>::value && __libcpp_is_trivially_equality_comparable<_Tp, _Up>::value &&
+                            sizeof(_Tp) == 1,
+                        int> = 0>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp*
+__find_impl(_Tp* __first, _Tp* __last, const _Up& __value, _Proj&) {
+  if (auto __ret = std::__constexpr_memchr(__first, __value, __last - __first))
+    return __ret;
+  return __last;
+}
+
+#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+template <class _Tp,
+          class _Up,
+          class _Proj,
+          __enable_if_t<__is_identity<_Proj>::value && __libcpp_is_trivially_equality_comparable<_Tp, _Up>::value &&
+                            sizeof(_Tp) == sizeof(wchar_t) && _LIBCPP_ALIGNOF(_Tp) >= _LIBCPP_ALIGNOF(wchar_t),
+                        int> = 0>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp*
+__find_impl(_Tp* __first, _Tp* __last, const _Up& __value, _Proj&) {
+  if (auto __ret = std::__constexpr_wmemchr(__first, __value, __last - __first))
+    return __ret;
+  return __last;
+}
+#endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS
+
+template <class _InputIterator, class _Tp>
+_LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 _InputIterator
+find(_InputIterator __first, _InputIterator __last, const _Tp& __value) {
+  __identity __proj;
+  return std::__rewrap_iter(
+      __first, std::__find_impl(std::__unwrap_iter(__first), std::__unwrap_iter(__last), __value, __proj));
+}
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ALGORITHM_FIND_H