368faacac7
This commit reverts 5aaefa51 (and also partly 7f285f48e77 and b6d75682f9, which were related to the original commit). As landed, 5aaefa51 had unintended consequences on some downstream bots and didn't have proper coverage upstream due to a few subtle things. Implementing this is something we should do in libc++, however we'll first need to address a few issues listed in https://reviews.llvm.org/D106124#3349710. Differential Revision: https://reviews.llvm.org/D120683
56 lines
1.7 KiB
C++
56 lines
1.7 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___BIT_BYTESWAP_H
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#define _LIBCPP___BIT_BYTESWAP_H
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#include <__concepts/arithmetic.h>
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#include <__config>
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#include <cstdint>
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#include <cstdlib>
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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_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER > 20 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
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template <integral _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp byteswap(_Tp __val) noexcept {
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if constexpr (sizeof(_Tp) == 1) {
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return __val;
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} else if constexpr (sizeof(_Tp) == 2) {
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return __builtin_bswap16(__val);
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} else if constexpr (sizeof(_Tp) == 4) {
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return __builtin_bswap32(__val);
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} else if constexpr (sizeof(_Tp) == 8) {
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return __builtin_bswap64(__val);
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#ifndef _LIBCPP_HAS_NO_INT128
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} else if constexpr (sizeof(_Tp) == 16) {
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#if __has_builtin(__builtin_bswap128)
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return __builtin_bswap128(__val);
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#else
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return static_cast<_Tp>(byteswap(static_cast<uint64_t>(__val))) << 64 |
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static_cast<_Tp>(byteswap(static_cast<uint64_t>(__val >> 64)));
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#endif // __has_builtin(__builtin_bswap128)
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#endif // _LIBCPP_HAS_NO_INT128
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} else {
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static_assert(sizeof(_Tp) == 0, "byteswap is unimplemented for integral types of this size");
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}
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}
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#endif // _LIBCPP_STD_VER > 20 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___BIT_BYTESWAP_H
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