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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support for C++03 for Zig due to the first change; it would be insane to ship 1018 duplicate header files just for this outdated use case.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.
72 lines
2.2 KiB
C++
Vendored
72 lines
2.2 KiB
C++
Vendored
//===----------------------------------------------------------------------===//
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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_ROTATE_H
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#define _LIBCPP___BIT_ROTATE_H
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#include <__concepts/arithmetic.h>
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#include <__config>
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#include <__type_traits/is_unsigned_integer.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_BEGIN_NAMESPACE_STD
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// Writing two full functions for rotl and rotr makes it easier for the compiler
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// to optimize the code. On x86 this function becomes the ROL instruction and
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// the rotr function becomes the ROR instruction.
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template <class _Tp>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp __rotl(_Tp __x, int __s) _NOEXCEPT {
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static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__rotl requires an unsigned integer type");
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const int __n = numeric_limits<_Tp>::digits;
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int __r = __s % __n;
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if (__r == 0)
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return __x;
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if (__r > 0)
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return (__x << __r) | (__x >> (__n - __r));
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return (__x >> -__r) | (__x << (__n + __r));
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}
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template <class _Tp>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp __rotr(_Tp __x, int __s) _NOEXCEPT {
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static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__rotr requires an unsigned integer type");
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const int __n = numeric_limits<_Tp>::digits;
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int __r = __s % __n;
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if (__r == 0)
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return __x;
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if (__r > 0)
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return (__x >> __r) | (__x << (__n - __r));
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return (__x << -__r) | (__x >> (__n + __r));
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}
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#if _LIBCPP_STD_VER >= 20
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template <__libcpp_unsigned_integer _Tp>
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp rotl(_Tp __t, int __cnt) noexcept {
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return std::__rotl(__t, __cnt);
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}
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template <__libcpp_unsigned_integer _Tp>
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp rotr(_Tp __t, int __cnt) noexcept {
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return std::__rotr(__t, __cnt);
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}
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#endif // _LIBCPP_STD_VER >= 20
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___BIT_ROTATE_H
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