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___BIT_ROTATE_H 10 #define _LIBCPP___BIT_ROTATE_H 11 12 #include <__concepts/arithmetic.h> 13 #include <__config> 14 #include <__type_traits/is_unsigned_integer.h> 15 #include <limits> 16 17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 18 # pragma GCC system_header 19 #endif 20 21 _LIBCPP_BEGIN_NAMESPACE_STD 22 23 // Writing two full functions for rotl and rotr makes it easier for the compiler 24 // to optimize the code. On x86 this function becomes the ROL instruction and 25 // the rotr function becomes the ROR instruction. 26 template <class _Tp> 27 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp __rotl(_Tp __x, int __s) _NOEXCEPT { 28 static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__rotl requires an unsigned integer type"); 29 const int __N = numeric_limits<_Tp>::digits; 30 int __r = __s % __N; 31 32 if (__r == 0) 33 return __x; 34 35 if (__r > 0) 36 return (__x << __r) | (__x >> (__N - __r)); 37 38 return (__x >> -__r) | (__x << (__N + __r)); 39 } 40 41 template <class _Tp> 42 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp __rotr(_Tp __x, int __s) _NOEXCEPT { 43 static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__rotr requires an unsigned integer type"); 44 const int __N = numeric_limits<_Tp>::digits; 45 int __r = __s % __N; 46 47 if (__r == 0) 48 return __x; 49 50 if (__r > 0) 51 return (__x >> __r) | (__x << (__N - __r)); 52 53 return (__x << -__r) | (__x >> (__N + __r)); 54 } 55 56 #if _LIBCPP_STD_VER >= 20 57 58 template <__libcpp_unsigned_integer _Tp> 59 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp rotl(_Tp __t, int __cnt) noexcept { 60 return std::__rotl(__t, __cnt); 61 } 62 63 template <__libcpp_unsigned_integer _Tp> 64 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp rotr(_Tp __t, int __cnt) noexcept { 65 return std::__rotr(__t, __cnt); 66 } 67 68 #endif // _LIBCPP_STD_VER >= 20 69 70 _LIBCPP_END_NAMESPACE_STD 71 72 #endif // _LIBCPP___BIT_ROTATE_H 73