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156ab87500
See: * https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc/77319 * https://discourse.llvm.org/t/rfc-project-hand-in-hand-llvm-libc-libc-code-sharing/77701 We're dropping support for C++03 for Zig due to the first change; it would be insane to ship 1018 duplicate header files just for this outdated use case. As a result of the second change, I had to bring in a subset of the headers from llvm-libc since libc++ now depends on these. Hopefully we can continue to get away with not copying the entirety of llvm-libc.
54 lines
1.6 KiB
C++
Vendored
54 lines
1.6 KiB
C++
Vendored
// -*- 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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#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 >= 23
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template <integral _Tp>
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[[nodiscard]] _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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# if _LIBCPP_HAS_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_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 >= 23
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___BIT_BYTESWAP_H
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