Implement vectorized min_ / max_element for ints

stl/inc/algorithm

@@ -18,7 +18,13 @@ _STL_DISABLE_CLANG_WARNINGS
 #undef new
 
 #if _USE_STD_VECTOR_ALGORITHMS
+
 _EXTERN_C
+struct _Min_max_element_t {
+    const void* _Min;
+    const void* _Max;
+};
+
 // The "noalias" attribute tells the compiler optimizer that pointers going into these hand-vectorized algorithms
 // won't be stored beyond the lifetime of the function, and that the function will only reference arrays denoted by
 // those pointers. The optimizer also assumes in that case that a pointer parameter is not returned to the caller via
@@ -34,7 +40,77 @@ __declspec(noalias) void __cdecl __std_reverse_copy_trivially_copyable_4(
     const void* _First, const void* _Last, void* _Dest) noexcept;
 __declspec(noalias) void __cdecl __std_reverse_copy_trivially_copyable_8(
     const void* _First, const void* _Last, void* _Dest) noexcept;
+
+const void* __stdcall __std_min_element_1(const void* _First, const void* _Last, bool _Signed) noexcept;
+const void* __stdcall __std_min_element_2(const void* _First, const void* _Last, bool _Signed) noexcept;
+const void* __stdcall __std_min_element_4(const void* _First, const void* _Last, bool _Signed) noexcept;
+const void* __stdcall __std_min_element_8(const void* _First, const void* _Last, bool _Signed) noexcept;
+
+const void* __stdcall __std_max_element_1(const void* _First, const void* _Last, bool _Signed) noexcept;
+const void* __stdcall __std_max_element_2(const void* _First, const void* _Last, bool _Signed) noexcept;
+const void* __stdcall __std_max_element_4(const void* _First, const void* _Last, bool _Signed) noexcept;
+const void* __stdcall __std_max_element_8(const void* _First, const void* _Last, bool _Signed) noexcept;
+
+_Min_max_element_t __stdcall __std_minmax_element_1(const void* _First, const void* _Last, bool _Signed) noexcept;
+_Min_max_element_t __stdcall __std_minmax_element_2(const void* _First, const void* _Last, bool _Signed) noexcept;
+_Min_max_element_t __stdcall __std_minmax_element_4(const void* _First, const void* _Last, bool _Signed) noexcept;
+_Min_max_element_t __stdcall __std_minmax_element_8(const void* _First, const void* _Last, bool _Signed) noexcept;
 _END_EXTERN_C
+
+template <class _Ty>
+_Ty* __std_min_element(_Ty* _First, _Ty* _Last) noexcept {
+    constexpr bool _Signed = _STD is_signed_v<_Ty>;
+
+    if constexpr (sizeof(_Ty) == 1) {
+        return const_cast<_Ty*>(static_cast<const _Ty*>(__std_min_element_1(_First, _Last, _Signed)));
+    } else if constexpr (sizeof(_Ty) == 2) {
+        return const_cast<_Ty*>(static_cast<const _Ty*>(__std_min_element_2(_First, _Last, _Signed)));
+    } else if constexpr (sizeof(_Ty) == 4) {
+        return const_cast<_Ty*>(static_cast<const _Ty*>(__std_min_element_4(_First, _Last, _Signed)));
+    } else if constexpr (sizeof(_Ty) == 8) {
+        return const_cast<_Ty*>(static_cast<const _Ty*>(__std_min_element_8(_First, _Last, _Signed)));
+    } else {
+        static_assert(_STD _Always_false<_Ty>, "Unexpected size");
+    }
+}
+
+template <class _Ty>
+_Ty* __std_max_element(_Ty* _First, _Ty* _Last) noexcept {
+    constexpr bool _Signed = _STD is_signed_v<_Ty>;
+
+    if constexpr (sizeof(_Ty) == 1) {
+        return const_cast<_Ty*>(static_cast<const _Ty*>(__std_max_element_1(_First, _Last, _Signed)));
+    } else if constexpr (sizeof(_Ty) == 2) {
+        return const_cast<_Ty*>(static_cast<const _Ty*>(__std_max_element_2(_First, _Last, _Signed)));
+    } else if constexpr (sizeof(_Ty) == 4) {
+        return const_cast<_Ty*>(static_cast<const _Ty*>(__std_max_element_4(_First, _Last, _Signed)));
+    } else if constexpr (sizeof(_Ty) == 8) {
+        return const_cast<_Ty*>(static_cast<const _Ty*>(__std_max_element_8(_First, _Last, _Signed)));
+    } else {
+        static_assert(_STD _Always_false<_Ty>, "Unexpected size");
+    }
+}
+
+template <class _Ty>
+_STD pair<_Ty*, _Ty*> __std_minmax_element(_Ty* _First, _Ty* _Last) noexcept {
+    constexpr bool _Signed = _STD is_signed_v<_Ty>;
+
+    _Min_max_element_t _Res;
+
+    if constexpr (sizeof(_Ty) == 1) {
+        _Res = __std_minmax_element_1(_First, _Last, _Signed);
+    } else if constexpr (sizeof(_Ty) == 2) {
+        _Res = __std_minmax_element_2(_First, _Last, _Signed);
+    } else if constexpr (sizeof(_Ty) == 4) {
+        _Res = __std_minmax_element_4(_First, _Last, _Signed);
+    } else if constexpr (sizeof(_Ty) == 8) {
+        _Res = __std_minmax_element_8(_First, _Last, _Signed);
+    } else {
+        static_assert(_STD _Always_false<_Ty>, "Unexpected size");
+    }
+
+    return {const_cast<_Ty*>(static_cast<const _Ty*>(_Res._Min)), const_cast<_Ty*>(static_cast<const _Ty*>(_Res._Max))};
+}
 #endif // _USE_STD_VECTOR_ALGORITHMS
 
 _STD_BEGIN
@@ -9297,8 +9373,33 @@ namespace ranges {
 #endif // __cpp_lib_concepts
 #endif // _HAS_CXX17
 
+template <class _Iter, class _Pr, class _Elem = _Iter_value_t<_Iter>>
+_INLINE_VAR constexpr bool _Is_min_max_optimization_safe = // Activate the vector algorithms for min_/max_element?
+    _Iterator_is_contiguous<_Iter> // The iterator must be contiguous so we can get raw pointers.
+    && !_Iterator_is_volatile<_Iter> // The iterator must not be volatile.
+    && conjunction_v<disjunction<is_integral<_Elem>, is_pointer<_Elem>>, // Element is of integral or pointer type.
+        disjunction< // And either of the following:
+#ifdef __cpp_lib_concepts
+            is_same<_Pr, _RANGES less>, // predicate is ranges::less
+#endif // __cpp_lib_concepts
+            is_same<_Pr, less<>>, is_same<_Pr, less<_Elem>>>>; // predicate is less
+
 template <class _FwdIt, class _Pr>
 constexpr _FwdIt _Max_element_unchecked(_FwdIt _First, _FwdIt _Last, _Pr _Pred) { // find largest element
+#if _USE_STD_VECTOR_ALGORITHMS
+    if constexpr (_Is_min_max_optimization_safe<_FwdIt, _Pr>) {
+        if (!_Is_constant_evaluated()) {
+            const auto _First_ptr = _To_address(_First);
+            const auto _Result    = __std_max_element(_First_ptr, _To_address(_Last));
+            if constexpr (is_pointer_v<_FwdIt>) {
+                return _Result;
+            } else {
+                return _First + (_Result - _First_ptr);
+            }
+        }
+    }
+#endif // _USE_STD_VECTOR_ALGORITHMS
+
     _FwdIt _Found = _First;
     if (_First != _Last) {
         while (++_First != _Last) {
@@ -9390,6 +9491,20 @@ namespace ranges {
 
 template <class _FwdIt, class _Pr>
 constexpr _FwdIt _Min_element_unchecked(_FwdIt _First, _FwdIt _Last, _Pr _Pred) { // find smallest element
+#if _USE_STD_VECTOR_ALGORITHMS
+    if constexpr (_Is_min_max_optimization_safe<_FwdIt, _Pr>) {
+        if (!_Is_constant_evaluated()) {
+            const auto _First_ptr = _To_address(_First);
+            const auto _Result    = __std_min_element(_First_ptr, _To_address(_Last));
+            if constexpr (is_pointer_v<_FwdIt>) {
+                return _Result;
+            } else {
+                return _First + (_Result - _First_ptr);
+            }
+        }
+    }
+#endif // _USE_STD_VECTOR_ALGORITHMS
+
     _FwdIt _Found = _First;
     if (_First != _Last) {
         while (++_First != _Last) {
@@ -9481,6 +9596,20 @@ namespace ranges {
 
 template <class _FwdIt, class _Pr>
 constexpr pair<_FwdIt, _FwdIt> _Minmax_element_unchecked(_FwdIt _First, _FwdIt _Last, _Pr _Pred) {
+#if _USE_STD_VECTOR_ALGORITHMS
+    if constexpr (_Is_min_max_optimization_safe<_FwdIt, _Pr>) {
+        if (!_Is_constant_evaluated()) {
+            const auto _First_ptr = _To_address(_First);
+            const auto _Result    = __std_minmax_element(_First_ptr, _To_address(_Last));
+            if constexpr (is_pointer_v<_FwdIt>) {
+                return _Result;
+            } else {
+                return {_First + (_Result.first - _First_ptr), _First + (_Result.second - _First_ptr)};
+            }
+        }
+    }
+#endif // _USE_STD_VECTOR_ALGORITHMS
+
     // find smallest and largest elements
     pair<_FwdIt, _FwdIt> _Found(_First, _First);
 

stl/inc/xtr1common

@@ -165,6 +165,10 @@ template <class _Ty, class... _Types>
 _INLINE_VAR constexpr bool _Is_any_of_v = // true if and only if _Ty is in _Types
     disjunction_v<is_same<_Ty, _Types>...>;
 
+_NODISCARD constexpr bool _Is_constant_evaluated() noexcept { // Internal function for any standard mode
+    return __builtin_is_constant_evaluated();
+}
+
 #if _HAS_CXX20
 _NODISCARD constexpr bool is_constant_evaluated() noexcept {
     return __builtin_is_constant_evaluated();