160 lines · cpp
1//===----------------------------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9// REQUIRES: std-at-least-c++2610 11// <numeric>12 13// template<class T>14// constexpr T sub_sat(T x, T y) noexcept; // freestanding15 16#include <cassert>17#include <concepts>18#include <limits>19#include <numeric>20 21#include "test_macros.h"22 23template <typename IntegerT>24constexpr bool test_signed() {25 constexpr auto minVal = std::numeric_limits<IntegerT>::min();26 constexpr auto maxVal = std::numeric_limits<IntegerT>::max();27 28 std::same_as<IntegerT> decltype(auto) _ = std::sub_sat(minVal, maxVal);29 30 static_assert(noexcept(std::sub_sat(minVal, maxVal)));31 32 // clang-format off33 34 // Limit values (-1, 0, 1, min, max)35 36 assert(std::sub_sat(IntegerT{-1}, IntegerT{-1}) == IntegerT{ 0});37 assert(std::sub_sat(IntegerT{-1}, IntegerT{ 0}) == IntegerT{-1});38 assert(std::sub_sat(IntegerT{-1}, IntegerT{ 1}) == IntegerT{-2});39 assert(std::sub_sat(IntegerT{-1}, minVal) == IntegerT{-1} - minVal);40 assert(std::sub_sat(IntegerT{-1}, maxVal) == IntegerT{-1} - maxVal);41 42 assert(std::sub_sat(IntegerT{ 0}, IntegerT{-1}) == IntegerT{ 1});43 assert(std::sub_sat(IntegerT{ 0}, IntegerT{ 0}) == IntegerT{ 0});44 assert(std::sub_sat(IntegerT{ 0}, IntegerT{ 1}) == IntegerT{-1});45 assert(std::sub_sat(IntegerT{ 0}, minVal) == maxVal); // saturated46 assert(std::sub_sat(IntegerT{ 0}, maxVal) == -maxVal);47 48 assert(std::sub_sat( minVal, IntegerT{-1}) == minVal - IntegerT{-1});49 assert(std::sub_sat( minVal, IntegerT{ 0}) == minVal);50 assert(std::sub_sat( minVal, IntegerT{ 1}) == minVal); // saturated51 assert(std::sub_sat( minVal, minVal) == IntegerT{0});52 assert(std::sub_sat( minVal, maxVal) == minVal); // saturated53 54 assert(std::sub_sat( maxVal, IntegerT{-1}) == maxVal); // saturated55 assert(std::sub_sat( maxVal, IntegerT{ 0}) == maxVal);56 assert(std::sub_sat( maxVal, IntegerT{ 1}) == maxVal - IntegerT{ 1});57 assert(std::sub_sat( maxVal, minVal) == maxVal); // saturated58 assert(std::sub_sat( maxVal, maxVal) == IntegerT{0});59 60 // No saturation (no limit values)61 62 assert(std::sub_sat(IntegerT{ 27}, IntegerT{-28}) == 55);63 assert(std::sub_sat(IntegerT{ 27}, IntegerT{ 28}) == -1);64 assert(std::sub_sat(IntegerT{-27}, IntegerT{ 28}) == -55);65 assert(std::sub_sat(IntegerT{-27}, IntegerT{-28}) == 1);66 67 // Saturation (no limit values)68 69 {70 constexpr IntegerT lesserVal = minVal / IntegerT{2} + IntegerT{27};71 constexpr IntegerT biggerVal = maxVal / IntegerT{2} + IntegerT{28};72 assert(std::sub_sat(lesserVal, biggerVal) == minVal); // saturated73 }74 {75 constexpr IntegerT biggerVal = maxVal / IntegerT{2} + IntegerT{28};76 constexpr IntegerT lesserVal = minVal / IntegerT{2} + IntegerT{27};77 assert(std::sub_sat(biggerVal, lesserVal) == maxVal); // saturated78 }79 80 // clang-format on81 82 return true;83}84 85template <typename IntegerT>86constexpr bool test_unsigned() {87 constexpr auto minVal = std::numeric_limits<IntegerT>::min();88 constexpr auto maxVal = std::numeric_limits<IntegerT>::max();89 90 std::same_as<IntegerT> decltype(auto) _ = std::sub_sat(minVal, maxVal);91 92 static_assert(noexcept(std::sub_sat(minVal, maxVal)));93 94 // clang-format off95 96 // Limit values (0, 1, min, max)97 98 assert(std::sub_sat(IntegerT{0}, IntegerT{0}) == IntegerT{0});99 assert(std::sub_sat(IntegerT{0}, IntegerT{1}) == minVal); // saturated100 assert(std::sub_sat(IntegerT{0}, minVal) == minVal);101 assert(std::sub_sat(IntegerT{0}, maxVal) == minVal); // saturated102 103 assert(std::sub_sat(IntegerT{1}, IntegerT{0}) == IntegerT{1});104 assert(std::sub_sat(IntegerT{1}, IntegerT{1}) == IntegerT{0});105 assert(std::sub_sat(IntegerT{1}, minVal) == IntegerT{1});106 assert(std::sub_sat(IntegerT{1}, maxVal) == minVal); // saturated107 108 assert(std::sub_sat( minVal, IntegerT{0}) == IntegerT{0});109 assert(std::sub_sat( minVal, IntegerT{1}) == minVal);110 assert(std::sub_sat( minVal, maxVal) == minVal);111 assert(std::sub_sat( minVal, maxVal) == minVal);112 113 assert(std::sub_sat( maxVal, IntegerT{0}) == maxVal);114 assert(std::sub_sat( maxVal, IntegerT{1}) == maxVal - IntegerT{1});115 assert(std::sub_sat( maxVal, minVal) == maxVal);116 assert(std::sub_sat( maxVal, maxVal) == IntegerT{0});117 118 // Saturation (no limit values)119 120 {121 constexpr IntegerT lesserVal = minVal / IntegerT{2} + IntegerT{27};122 constexpr IntegerT biggerVal = maxVal / IntegerT{2} + IntegerT{28};123 assert(std::sub_sat(lesserVal, biggerVal) == minVal); // saturated124 }125 126 // clang-format on127 128 return true;129}130 131constexpr bool test() {132 // Signed133 test_signed<signed char>();134 test_signed<short int>();135 test_signed<int>();136 test_signed<long int>();137 test_signed<long long int>();138#ifndef TEST_HAS_NO_INT128139 test_signed<__int128_t>();140#endif141 // Unsigned142 test_unsigned<unsigned char>();143 test_unsigned<unsigned short int>();144 test_unsigned<unsigned int>();145 test_unsigned<unsigned long int>();146 test_unsigned<unsigned long long int>();147#ifndef TEST_HAS_NO_INT128148 test_unsigned<__uint128_t>();149#endif150 151 return true;152}153 154int main(int, char**) {155 test();156 static_assert(test());157 158 return 0;159}160