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 <__concepts/arithmetic.h>
15#include <__config>
16#include <__utility/cmp.h>
17#include <limits>
18
19#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20# pragma GCC system_header
21#endif
22
23_LIBCPP_PUSH_MACROS
24#include <__undef_macros>
25
26_LIBCPP_BEGIN_NAMESPACE_STD
27
28#if _LIBCPP_STD_VER >= 20
29
30template <__libcpp_integer _Tp>
31_LIBCPP_HIDE_FROM_ABI constexpr _Tp __add_sat(_Tp __x, _Tp __y) noexcept {
32 if (_Tp __sum; !__builtin_add_overflow(__x, __y, &__sum))
33 return __sum;
34 // Handle overflow
35 if constexpr (__libcpp_unsigned_integer<_Tp>) {
36 return std::numeric_limits<_Tp>::max();
37 } else {
38 // Signed addition overflow
39 if (__x > 0)
40 // Overflows if (x > 0 && y > 0)
41 return std::numeric_limits<_Tp>::max();
42 else
43 // Overflows if (x < 0 && y < 0)
44 return std::numeric_limits<_Tp>::min();
45 }
46}
47
48template <__libcpp_integer _Tp>
49_LIBCPP_HIDE_FROM_ABI constexpr _Tp __sub_sat(_Tp __x, _Tp __y) noexcept {
50 if (_Tp __sub; !__builtin_sub_overflow(__x, __y, &__sub))
51 return __sub;
52 // Handle overflow
53 if constexpr (__libcpp_unsigned_integer<_Tp>) {
54 // Overflows if (x < y)
55 return std::numeric_limits<_Tp>::min();
56 } else {
57 // Signed subtration overflow
58 if (__x >= 0)
59 // Overflows if (x >= 0 && y < 0)
60 return std::numeric_limits<_Tp>::max();
61 else
62 // Overflows if (x < 0 && y > 0)
63 return std::numeric_limits<_Tp>::min();
64 }
65}
66
67template <__libcpp_integer _Tp>
68_LIBCPP_HIDE_FROM_ABI constexpr _Tp __mul_sat(_Tp __x, _Tp __y) noexcept {
69 if (_Tp __mul; !__builtin_mul_overflow(__x, __y, &__mul))
70 return __mul;
71 // Handle overflow
72 if constexpr (__libcpp_unsigned_integer<_Tp>) {
73 return std::numeric_limits<_Tp>::max();
74 } else {
75 // Signed multiplication overflow
76 if ((__x > 0 && __y > 0) || (__x < 0 && __y < 0))
77 return std::numeric_limits<_Tp>::max();
78 // Overflows if (x < 0 && y > 0) || (x > 0 && y < 0)
79 return std::numeric_limits<_Tp>::min();
80 }
81}
82
83template <__libcpp_integer _Tp>
84_LIBCPP_HIDE_FROM_ABI constexpr _Tp __div_sat(_Tp __x, _Tp __y) noexcept {
85 _LIBCPP_ASSERT_UNCATEGORIZED(__y != 0, "Division by 0 is undefined");
86 if constexpr (__libcpp_unsigned_integer<_Tp>) {
87 return __x / __y;
88 } else {
89 // Handle signed division overflow
90 if (__x == std::numeric_limits<_Tp>::min() && __y == _Tp{-1})
91 return std::numeric_limits<_Tp>::max();
92 return __x / __y;
93 }
94}
95
96template <__libcpp_integer _Rp, __libcpp_integer _Tp>
97_LIBCPP_HIDE_FROM_ABI constexpr _Rp __saturate_cast(_Tp __x) noexcept {
98 // Saturation is impossible edge case when ((min _Rp) < (min _Tp) && (max _Rp) > (max _Tp)) and it is expected to be
99 // optimized out by the compiler.
100
101 // Handle overflow
102 if (std::cmp_less(__x, std::numeric_limits<_Rp>::min()))
103 return std::numeric_limits<_Rp>::min();
104 if (std::cmp_greater(__x, std::numeric_limits<_Rp>::max()))
105 return std::numeric_limits<_Rp>::max();
106 // No overflow
107 return static_cast<_Rp>(__x);
108}
109
110#endif // _LIBCPP_STD_VER >= 20
111
112#if _LIBCPP_STD_VER >= 26
113
114template <__libcpp_integer _Tp>
115_LIBCPP_HIDE_FROM_ABI constexpr _Tp add_sat(_Tp __x, _Tp __y) noexcept {
116 return std::__add_sat(__x, __y);
117}
118
119template <__libcpp_integer _Tp>
120_LIBCPP_HIDE_FROM_ABI constexpr _Tp sub_sat(_Tp __x, _Tp __y) noexcept {
121 return std::__sub_sat(__x, __y);
122}
123
124template <__libcpp_integer _Tp>
125_LIBCPP_HIDE_FROM_ABI constexpr _Tp mul_sat(_Tp __x, _Tp __y) noexcept {
126 return std::__mul_sat(__x, __y);
127}
128
129template <__libcpp_integer _Tp>
130_LIBCPP_HIDE_FROM_ABI constexpr _Tp div_sat(_Tp __x, _Tp __y) noexcept {
131 return std::__div_sat(__x, __y);
132}
133
134template <__libcpp_integer _Rp, __libcpp_integer _Tp>
135_LIBCPP_HIDE_FROM_ABI constexpr _Rp saturate_cast(_Tp __x) noexcept {
136 return std::__saturate_cast<_Rp>(__x);
137}
138
139#endif // _LIBCPP_STD_VER >= 26
140
141_LIBCPP_END_NAMESPACE_STD
142
143_LIBCPP_POP_MACROS
144
145#endif // _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
146