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| 1 | //===----------------------------------------------------------------------===// |
|---|---|
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #ifndef _LIBCPP___CXX03___BIT_ROTATE_H |
| 10 | #define _LIBCPP___CXX03___BIT_ROTATE_H |
| 11 | |
| 12 | #include <__cxx03/__config> |
| 13 | #include <__cxx03/__type_traits/is_unsigned_integer.h> |
| 14 | #include <__cxx03/limits> |
| 15 | |
| 16 | #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| 17 | # pragma GCC system_header |
| 18 | #endif |
| 19 | |
| 20 | _LIBCPP_BEGIN_NAMESPACE_STD |
| 21 | |
| 22 | // Writing two full functions for rotl and rotr makes it easier for the compiler |
| 23 | // to optimize the code. On x86 this function becomes the ROL instruction and |
| 24 | // the rotr function becomes the ROR instruction. |
| 25 | template <class _Tp> |
| 26 | _LIBCPP_HIDE_FROM_ABI _Tp __rotl(_Tp __x, int __s) _NOEXCEPT { |
| 27 | static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__rotl requires an unsigned integer type"); |
| 28 | const int __N = numeric_limits<_Tp>::digits; |
| 29 | int __r = __s % __N; |
| 30 | |
| 31 | if (__r == 0) |
| 32 | return __x; |
| 33 | |
| 34 | if (__r > 0) |
| 35 | return (__x << __r) | (__x >> (__N - __r)); |
| 36 | |
| 37 | return (__x >> -__r) | (__x << (__N + __r)); |
| 38 | } |
| 39 | |
| 40 | template <class _Tp> |
| 41 | _LIBCPP_HIDE_FROM_ABI _Tp __rotr(_Tp __x, int __s) _NOEXCEPT { |
| 42 | static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__rotr requires an unsigned integer type"); |
| 43 | const int __N = numeric_limits<_Tp>::digits; |
| 44 | int __r = __s % __N; |
| 45 | |
| 46 | if (__r == 0) |
| 47 | return __x; |
| 48 | |
| 49 | if (__r > 0) |
| 50 | return (__x >> __r) | (__x << (__N - __r)); |
| 51 | |
| 52 | return (__x << -__r) | (__x >> (__N + __r)); |
| 53 | } |
| 54 | |
| 55 | _LIBCPP_END_NAMESPACE_STD |
| 56 | |
| 57 | #endif // _LIBCPP___CXX03___BIT_ROTATE_H |
| 58 |
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