[libc++] Fix build issues and replace std::find with loop

[libcxx] revert block_size logic

[libc++] Replace std::find with impl

Author: mrdaybird

libcxx/include/__algorithm/find.h

@@ -106,7 +106,7 @@ __find_bool(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n)
   // do first partial word
   if (__first.__ctz_ != 0) {
     __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
-    __storage_type __dn    = (__clz_f < __n) ? __clz_f : __n;
+    __storage_type __dn    = std::min(__clz_f, __n);
     __storage_type __m     = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
     __storage_type __b     = std::__invert_if<!_ToFind>(*__first.__seg_) & __m;
     if (__b)

libcxx/include/__algorithm/min_element.h

@@ -11,7 +11,6 @@
 
 #include <__algorithm/comp.h>
 #include <__algorithm/comp_ref_type.h>
-#include <__algorithm/find.h>
 #include <__algorithm/iterator_operations.h>
 #include <__config>
 #include <__functional/identity.h>
@@ -29,13 +28,54 @@ _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(
+    _Iter __first,
+    _Sent __last,
+    _Comp __comp,
+    _Proj& __proj,
+    /*_ConstTimeDistance*/ false_type) {
   if (__first == __last)
     return __first;
 
-  const size_t __n = static_cast<size_t>(std::distance(__first, __last));
+  _Iter __i = __first;
+  while (++__i != __last)
+    if (std::__invoke(__comp, std::__invoke(__proj, *__i), std::__invoke(__proj, *__first)))
+      __first = __i;
+  return __first;
+}
+
+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,
+    /*ConstTimeDistance*/ true_type) {
+  if (__first == __last)
+    return __first;
+
+  typedef typename std::iterator_traits<_Iter>::difference_type diff_type;
+  diff_type __n = std::distance(__first, __last);
 
   if (__n <= 64) {
     _Iter __i = __first;
@@ -45,19 +85,19 @@ __min_element(_Iter __first, _Sent __last, _Comp __comp, _Proj& __proj) {
     return __first;
   }
 
-  size_t __block_size = 256;
+  diff_type __block_size = 256;
 
-  size_t __n_blocked  = __n - (__n % __block_size);
+  diff_type __n_blocked = __n - (__n % __block_size);
   _Iter __block_start = __first, __block_end = __first;
 
   typedef typename std::iterator_traits<_Iter>::value_type value_type;
   value_type __min_val = std::__invoke(__proj, *__first);
 
   _Iter __curr = __first;
-  for (size_t __i = 0; __i < __n_blocked; __i += __block_size) {
+  for (diff_type __i = 0; __i < __n_blocked; __i += __block_size) {
     _Iter __start          = __curr;
     value_type __block_min = __min_val;
-    for (size_t j = 0; j < __block_size; j++) {
+    for (diff_type __j = 0; __j < __block_size; __j++) {
       if (std::__invoke(__comp, std::__invoke(__proj, *__curr), __block_min)) {
         __block_min = *__curr;
       }
@@ -84,7 +124,17 @@ __min_element(_Iter __first, _Sent __last, _Comp __comp, _Proj& __proj) {
     __block_end   = __last;
   }
 
-  return std::__find(__block_start, __block_end, __min_val, __proj);
+  for (; __block_start != __block_end; ++__block_start)
+    if (std::__invoke(__proj, *__block_start) == __min_val)
+      break;
+  return __block_start;
+}
+
+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) {
+  return std::__min_element<_Comp>(
+      std::move(__first), std::move(__last), __comp, __proj, __ConstTimeDistance<_Iter, _Sent>());
 }
 
 template <class _Comp, class _Iter, class _Sent>