d4222bf9e2
This doesn't improve performance (except with optimizations disabled), since the compiler is able to fold our current implementation. However, it does significantly reduce the amount of code the compiler has to sift through, reducing compile times a bit.
155 lines
4.8 KiB
C++
155 lines
4.8 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
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#define _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
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#include <__assert>
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#include <__config>
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#include <__memory/addressof.h>
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#include <__type_traits/integer_traits.h>
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#include <__utility/cmp.h>
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#include <limits>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER >= 20
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template <__signed_or_unsigned_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp __add_sat(_Tp __x, _Tp __y) noexcept {
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# if defined(_LIBCPP_CLANG_VER) && _LIBCPP_CLANG_VER >= 2101
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return __builtin_elementwise_add_sat(__x, __y);
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# else
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if (_Tp __sum; !__builtin_add_overflow(__x, __y, std::addressof(__sum)))
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return __sum;
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// Handle overflow
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if constexpr (__unsigned_integer<_Tp>) {
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return std::numeric_limits<_Tp>::max();
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} else {
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// Signed addition overflow
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if (__x > 0)
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// Overflows if (x > 0 && y > 0)
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return std::numeric_limits<_Tp>::max();
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else
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// Overflows if (x < 0 && y < 0)
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return std::numeric_limits<_Tp>::min();
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}
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# endif
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}
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template <__signed_or_unsigned_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp __sub_sat(_Tp __x, _Tp __y) noexcept {
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# if defined(_LIBCPP_CLANG_VER) && _LIBCPP_CLANG_VER >= 2101
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return __builtin_elementwise_sub_sat(__x, __y);
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# else
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if (_Tp __sub; !__builtin_sub_overflow(__x, __y, std::addressof(__sub)))
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return __sub;
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// Handle overflow
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if constexpr (__unsigned_integer<_Tp>) {
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// Overflows if (x < y)
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return std::numeric_limits<_Tp>::min();
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} else {
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// Signed subtration overflow
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if (__x >= 0)
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// Overflows if (x >= 0 && y < 0)
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return std::numeric_limits<_Tp>::max();
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else
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// Overflows if (x < 0 && y > 0)
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return std::numeric_limits<_Tp>::min();
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}
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# endif
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}
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template <__signed_or_unsigned_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp __mul_sat(_Tp __x, _Tp __y) noexcept {
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if (_Tp __mul; !__builtin_mul_overflow(__x, __y, std::addressof(__mul)))
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return __mul;
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// Handle overflow
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if constexpr (__unsigned_integer<_Tp>) {
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return std::numeric_limits<_Tp>::max();
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} else {
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// Signed multiplication overflow
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if ((__x > 0 && __y > 0) || (__x < 0 && __y < 0))
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return std::numeric_limits<_Tp>::max();
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// Overflows if (x < 0 && y > 0) || (x > 0 && y < 0)
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return std::numeric_limits<_Tp>::min();
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}
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}
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template <__signed_or_unsigned_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp __div_sat(_Tp __x, _Tp __y) noexcept {
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_LIBCPP_ASSERT_UNCATEGORIZED(__y != 0, "Division by 0 is undefined");
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if constexpr (__unsigned_integer<_Tp>) {
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return __x / __y;
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} else {
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// Handle signed division overflow
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if (__x == std::numeric_limits<_Tp>::min() && __y == _Tp{-1})
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return std::numeric_limits<_Tp>::max();
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return __x / __y;
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}
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}
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template <__signed_or_unsigned_integer _Rp, __signed_or_unsigned_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Rp __saturate_cast(_Tp __x) noexcept {
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// Saturation is impossible edge case when ((min _Rp) < (min _Tp) && (max _Rp) > (max _Tp)) and it is expected to be
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// optimized out by the compiler.
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// Handle overflow
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if (std::cmp_less(__x, std::numeric_limits<_Rp>::min()))
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return std::numeric_limits<_Rp>::min();
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if (std::cmp_greater(__x, std::numeric_limits<_Rp>::max()))
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return std::numeric_limits<_Rp>::max();
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// No overflow
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return static_cast<_Rp>(__x);
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}
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#endif // _LIBCPP_STD_VER >= 20
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#if _LIBCPP_STD_VER >= 26
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template <__signed_or_unsigned_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp add_sat(_Tp __x, _Tp __y) noexcept {
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return std::__add_sat(__x, __y);
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}
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template <__signed_or_unsigned_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp sub_sat(_Tp __x, _Tp __y) noexcept {
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return std::__sub_sat(__x, __y);
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}
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template <__signed_or_unsigned_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp mul_sat(_Tp __x, _Tp __y) noexcept {
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return std::__mul_sat(__x, __y);
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}
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template <__signed_or_unsigned_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp div_sat(_Tp __x, _Tp __y) noexcept {
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return std::__div_sat(__x, __y);
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}
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template <__signed_or_unsigned_integer _Rp, __signed_or_unsigned_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Rp saturate_cast(_Tp __x) noexcept {
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return std::__saturate_cast<_Rp>(__x);
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}
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#endif // _LIBCPP_STD_VER >= 26
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
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