forked from OSchip/llvm-project
137 lines
6.3 KiB
C++
137 lines
6.3 KiB
C++
//===----------------------------------------------------------------------===//
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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___COMPARE_STRONG_ORDER
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#define _LIBCPP___COMPARE_STRONG_ORDER
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#include <__bit/bit_cast.h>
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#include <__compare/compare_three_way.h>
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#include <__compare/ordering.h>
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#include <__config>
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#include <__utility/forward.h>
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#include <__utility/priority_tag.h>
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#include <cmath>
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#include <cstdint>
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#include <limits>
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#include <type_traits>
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#ifndef _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 > 17
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// [cmp.alg]
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namespace __strong_order {
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struct __fn {
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template<class _Tp, class _Up>
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requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
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_LIBCPP_HIDE_FROM_ABI static constexpr auto
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__go(_Tp&& __t, _Up&& __u, __priority_tag<2>)
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noexcept(noexcept(strong_ordering(strong_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))))
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-> decltype( strong_ordering(strong_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
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{ return strong_ordering(strong_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))); }
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template<class _Tp, class _Up, class _Dp = decay_t<_Tp>>
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requires is_same_v<_Dp, decay_t<_Up>> && is_floating_point_v<_Dp>
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_LIBCPP_HIDE_FROM_ABI static constexpr strong_ordering
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__go(_Tp&& __t, _Up&& __u, __priority_tag<1>) noexcept
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{
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if constexpr (numeric_limits<_Dp>::is_iec559 && sizeof(_Dp) == sizeof(int32_t)) {
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int32_t __rx = _VSTD::bit_cast<int32_t>(__t);
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int32_t __ry = _VSTD::bit_cast<int32_t>(__u);
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__rx = (__rx < 0) ? (numeric_limits<int32_t>::min() - __rx - 1) : __rx;
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__ry = (__ry < 0) ? (numeric_limits<int32_t>::min() - __ry - 1) : __ry;
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return (__rx <=> __ry);
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} else if constexpr (numeric_limits<_Dp>::is_iec559 && sizeof(_Dp) == sizeof(int64_t)) {
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int64_t __rx = _VSTD::bit_cast<int64_t>(__t);
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int64_t __ry = _VSTD::bit_cast<int64_t>(__u);
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__rx = (__rx < 0) ? (numeric_limits<int64_t>::min() - __rx - 1) : __rx;
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__ry = (__ry < 0) ? (numeric_limits<int64_t>::min() - __ry - 1) : __ry;
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return (__rx <=> __ry);
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} else if (__t < __u) {
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return strong_ordering::less;
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} else if (__t > __u) {
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return strong_ordering::greater;
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} else if (__t == __u) {
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if constexpr (numeric_limits<_Dp>::radix == 2) {
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return _VSTD::signbit(__u) <=> _VSTD::signbit(__t);
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} else {
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// This is bullet 3 of the IEEE754 algorithm, relevant
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// only for decimal floating-point;
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// see https://stackoverflow.com/questions/69068075/
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if (__t == 0 || _VSTD::isinf(__t)) {
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return _VSTD::signbit(__u) <=> _VSTD::signbit(__t);
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} else {
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int __texp, __uexp;
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(void)_VSTD::frexp(__t, &__texp);
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(void)_VSTD::frexp(__u, &__uexp);
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return (__t < 0) ? (__texp <=> __uexp) : (__uexp <=> __texp);
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}
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}
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} else {
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// They're unordered, so one of them must be a NAN.
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// The order is -QNAN, -SNAN, numbers, +SNAN, +QNAN.
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bool __t_is_nan = _VSTD::isnan(__t);
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bool __u_is_nan = _VSTD::isnan(__u);
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bool __t_is_negative = _VSTD::signbit(__t);
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bool __u_is_negative = _VSTD::signbit(__u);
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using _IntType = conditional_t<
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sizeof(__t) == sizeof(int32_t), int32_t, conditional_t<
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sizeof(__t) == sizeof(int64_t), int64_t, void>
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>;
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if constexpr (is_same_v<_IntType, void>) {
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static_assert(sizeof(_Dp) == 0, "std::strong_order is unimplemented for this floating-point type");
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} else if (__t_is_nan && __u_is_nan) {
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// Order by sign bit, then by "payload bits" (we'll just use bit_cast).
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if (__t_is_negative != __u_is_negative) {
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return (__u_is_negative <=> __t_is_negative);
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} else {
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return _VSTD::bit_cast<_IntType>(__t) <=> _VSTD::bit_cast<_IntType>(__u);
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}
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} else if (__t_is_nan) {
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return __t_is_negative ? strong_ordering::less : strong_ordering::greater;
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} else {
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return __u_is_negative ? strong_ordering::greater : strong_ordering::less;
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}
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}
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}
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template<class _Tp, class _Up>
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requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
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_LIBCPP_HIDE_FROM_ABI static constexpr auto
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__go(_Tp&& __t, _Up&& __u, __priority_tag<0>)
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noexcept(noexcept(strong_ordering(compare_three_way()(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))))
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-> decltype( strong_ordering(compare_three_way()(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
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{ return strong_ordering(compare_three_way()(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))); }
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template<class _Tp, class _Up>
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_LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
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noexcept(noexcept(__go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<2>())))
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-> decltype( __go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<2>()))
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{ return __go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<2>()); }
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};
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} // namespace __strong_order
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inline namespace __cpo {
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inline constexpr auto strong_order = __strong_order::__fn{};
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} // namespace __cpo
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#endif // _LIBCPP_STD_VER > 17
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___COMPARE_STRONG_ORDER
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