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.
26template <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
41template <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
58template <__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
63template <__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