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 (_Tp __sum; !__builtin_add_overflow(__x, __y, std::addressof(__sum)))
34 return __sum;
35 // Handle overflow
36 if constexpr (__unsigned_integer<_Tp>) {
37 return std::numeric_limits<_Tp>::max();
38 } else {
39 // Signed addition overflow
40 if (__x > 0)
41 // Overflows if (x > 0 && y > 0)
42 return std::numeric_limits<_Tp>::max();
43 else
44 // Overflows if (x < 0 && y < 0)
45 return std::numeric_limits<_Tp>::min();
46 }
47}
48
49template <__signed_or_unsigned_integer _Tp>
50_LIBCPP_HIDE_FROM_ABI constexpr _Tp __sub_sat(_Tp __x, _Tp __y) noexcept {
51 if (_Tp __sub; !__builtin_sub_overflow(__x, __y, std::addressof(__sub)))
52 return __sub;
53 // Handle overflow
54 if constexpr (__unsigned_integer<_Tp>) {
55 // Overflows if (x < y)
56 return std::numeric_limits<_Tp>::min();
57 } else {
58 // Signed subtration overflow
59 if (__x >= 0)
60 // Overflows if (x >= 0 && y < 0)
61 return std::numeric_limits<_Tp>::max();
62 else
63 // Overflows if (x < 0 && y > 0)
64 return std::numeric_limits<_Tp>::min();
65 }
66}
67
68template <__signed_or_unsigned_integer _Tp>
69_LIBCPP_HIDE_FROM_ABI constexpr _Tp __mul_sat(_Tp __x, _Tp __y) noexcept {
70 if (_Tp __mul; !__builtin_mul_overflow(__x, __y, std::addressof(__mul)))
71 return __mul;
72 // Handle overflow
73 if constexpr (__unsigned_integer<_Tp>) {
74 return std::numeric_limits<_Tp>::max();
75 } else {
76 // Signed multiplication overflow
77 if ((__x > 0 && __y > 0) || (__x < 0 && __y < 0))
78 return std::numeric_limits<_Tp>::max();
79 // Overflows if (x < 0 && y > 0) || (x > 0 && y < 0)
80 return std::numeric_limits<_Tp>::min();
81 }
82}
83
84template <__signed_or_unsigned_integer _Tp>
85_LIBCPP_HIDE_FROM_ABI constexpr _Tp __div_sat(_Tp __x, _Tp __y) noexcept {
86 _LIBCPP_ASSERT_UNCATEGORIZED(__y != 0, "Division by 0 is undefined");
87 if constexpr (__unsigned_integer<_Tp>) {
88 return __x / __y;
89 } else {
90 // Handle signed division overflow
91 if (__x == std::numeric_limits<_Tp>::min() && __y == _Tp{-1})
92 return std::numeric_limits<_Tp>::max();
93 return __x / __y;
94 }
95}
96
97template <__signed_or_unsigned_integer _Rp, __signed_or_unsigned_integer _Tp>
98_LIBCPP_HIDE_FROM_ABI constexpr _Rp __saturate_cast(_Tp __x) noexcept {
99 // Saturation is impossible edge case when ((min _Rp) < (min _Tp) && (max _Rp) > (max _Tp)) and it is expected to be
100 // optimized out by the compiler.
101
102 // Handle overflow
103 if (std::cmp_less(__x, std::numeric_limits<_Rp>::min()))
104 return std::numeric_limits<_Rp>::min();
105 if (std::cmp_greater(__x, std::numeric_limits<_Rp>::max()))
106 return std::numeric_limits<_Rp>::max();
107 // No overflow
108 return static_cast<_Rp>(__x);
109}
110
111#endif // _LIBCPP_STD_VER >= 20
112
113#if _LIBCPP_STD_VER >= 26
114
115template <__signed_or_unsigned_integer _Tp>
116_LIBCPP_HIDE_FROM_ABI constexpr _Tp add_sat(_Tp __x, _Tp __y) noexcept {
117 return std::__add_sat(__x, __y);
118}
119
120template <__signed_or_unsigned_integer _Tp>
121_LIBCPP_HIDE_FROM_ABI constexpr _Tp sub_sat(_Tp __x, _Tp __y) noexcept {
122 return std::__sub_sat(__x, __y);
123}
124
125template <__signed_or_unsigned_integer _Tp>
126_LIBCPP_HIDE_FROM_ABI constexpr _Tp mul_sat(_Tp __x, _Tp __y) noexcept {
127 return std::__mul_sat(__x, __y);
128}
129
130template <__signed_or_unsigned_integer _Tp>
131_LIBCPP_HIDE_FROM_ABI constexpr _Tp div_sat(_Tp __x, _Tp __y) noexcept {
132 return std::__div_sat(__x, __y);
133}
134
135template <__signed_or_unsigned_integer _Rp, __signed_or_unsigned_integer _Tp>
136_LIBCPP_HIDE_FROM_ABI constexpr _Rp saturate_cast(_Tp __x) noexcept {
137 return std::__saturate_cast<_Rp>(__x);
138}
139
140#endif // _LIBCPP_STD_VER >= 26
141
142_LIBCPP_END_NAMESPACE_STD
143
144_LIBCPP_POP_MACROS
145
146#endif // _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
147