1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
11#define _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
12
13#include <__assert>
14#include <__config>
15#include <__memory/addressof.h>
16#include <__type_traits/integer_traits.h>
17#include <__utility/cmp.h>
18#include <limits>
19
20#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
21# pragma GCC system_header
22#endif
23
24_LIBCPP_PUSH_MACROS
25#include <__undef_macros>
26
27_LIBCPP_BEGIN_NAMESPACE_STD
28
29#if _LIBCPP_STD_VER >= 20
30
31template <__signed_or_unsigned_integer _Tp>
32_LIBCPP_HIDE_FROM_ABI constexpr _Tp __add_sat(_Tp __x, _Tp __y) noexcept {
33# if defined(_LIBCPP_CLANG_VER) && _LIBCPP_CLANG_VER >= 2101
34 return __builtin_elementwise_add_sat(__x, __y);
35# else
36 if (_Tp __sum; !__builtin_add_overflow(__x, __y, std::addressof(__sum)))
37 return __sum;
38 // Handle overflow
39 if constexpr (__unsigned_integer<_Tp>) {
40 return std::numeric_limits<_Tp>::max();
41 } else {
42 // Signed addition overflow
43 if (__x > 0)
44 // Overflows if (x > 0 && y > 0)
45 return std::numeric_limits<_Tp>::max();
46 else
47 // Overflows if (x < 0 && y < 0)
48 return std::numeric_limits<_Tp>::min();
49 }
50# endif
51}
52
53template <__signed_or_unsigned_integer _Tp>
54_LIBCPP_HIDE_FROM_ABI constexpr _Tp __sub_sat(_Tp __x, _Tp __y) noexcept {
55# if defined(_LIBCPP_CLANG_VER) && _LIBCPP_CLANG_VER >= 2101
56 return __builtin_elementwise_sub_sat(__x, __y);
57# else
58 if (_Tp __sub; !__builtin_sub_overflow(__x, __y, std::addressof(__sub)))
59 return __sub;
60 // Handle overflow
61 if constexpr (__unsigned_integer<_Tp>) {
62 // Overflows if (x < y)
63 return std::numeric_limits<_Tp>::min();
64 } else {
65 // Signed subtration overflow
66 if (__x >= 0)
67 // Overflows if (x >= 0 && y < 0)
68 return std::numeric_limits<_Tp>::max();
69 else
70 // Overflows if (x < 0 && y > 0)
71 return std::numeric_limits<_Tp>::min();
72 }
73# endif
74}
75
76template <__signed_or_unsigned_integer _Tp>
77_LIBCPP_HIDE_FROM_ABI constexpr _Tp __mul_sat(_Tp __x, _Tp __y) noexcept {
78 if (_Tp __mul; !__builtin_mul_overflow(__x, __y, std::addressof(__mul)))
79 return __mul;
80 // Handle overflow
81 if constexpr (__unsigned_integer<_Tp>) {
82 return std::numeric_limits<_Tp>::max();
83 } else {
84 // Signed multiplication overflow
85 if ((__x > 0 && __y > 0) || (__x < 0 && __y < 0))
86 return std::numeric_limits<_Tp>::max();
87 // Overflows if (x < 0 && y > 0) || (x > 0 && y < 0)
88 return std::numeric_limits<_Tp>::min();
89 }
90}
91
92template <__signed_or_unsigned_integer _Tp>
93_LIBCPP_HIDE_FROM_ABI constexpr _Tp __div_sat(_Tp __x, _Tp __y) noexcept {
94 _LIBCPP_ASSERT_UNCATEGORIZED(__y != 0, "Division by 0 is undefined");
95 if constexpr (__unsigned_integer<_Tp>) {
96 return __x / __y;
97 } else {
98 // Handle signed division overflow
99 if (__x == std::numeric_limits<_Tp>::min() && __y == _Tp{-1})
100 return std::numeric_limits<_Tp>::max();
101 return __x / __y;
102 }
103}
104
105template <__signed_or_unsigned_integer _Rp, __signed_or_unsigned_integer _Tp>
106_LIBCPP_HIDE_FROM_ABI constexpr _Rp __saturate_cast(_Tp __x) noexcept {
107 // Saturation is impossible edge case when ((min _Rp) < (min _Tp) && (max _Rp) > (max _Tp)) and it is expected to be
108 // optimized out by the compiler.
109
110 // Handle overflow
111 if (std::cmp_less(__x, std::numeric_limits<_Rp>::min()))
112 return std::numeric_limits<_Rp>::min();
113 if (std::cmp_greater(__x, std::numeric_limits<_Rp>::max()))
114 return std::numeric_limits<_Rp>::max();
115 // No overflow
116 return static_cast<_Rp>(__x);
117}
118
119#endif // _LIBCPP_STD_VER >= 20
120
121#if _LIBCPP_STD_VER >= 26
122
123template <__signed_or_unsigned_integer _Tp>
124[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp add_sat(_Tp __x, _Tp __y) noexcept {
125 return std::__add_sat(__x, __y);
126}
127
128template <__signed_or_unsigned_integer _Tp>
129[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp sub_sat(_Tp __x, _Tp __y) noexcept {
130 return std::__sub_sat(__x, __y);
131}
132
133template <__signed_or_unsigned_integer _Tp>
134[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp mul_sat(_Tp __x, _Tp __y) noexcept {
135 return std::__mul_sat(__x, __y);
136}
137
138template <__signed_or_unsigned_integer _Tp>
139[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp div_sat(_Tp __x, _Tp __y) noexcept {
140 return std::__div_sat(__x, __y);
141}
142
143template <__signed_or_unsigned_integer _Rp, __signed_or_unsigned_integer _Tp>
144[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Rp saturate_cast(_Tp __x) noexcept {
145 return std::__saturate_cast<_Rp>(__x);
146}
147
148#endif // _LIBCPP_STD_VER >= 26
149
150_LIBCPP_END_NAMESPACE_STD
151
152_LIBCPP_POP_MACROS
153
154#endif // _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
155