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>
__rotl(_Tp __x,int __s)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>
__rotr(_Tp __x,int __s)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>
rotl(_Tp __t,int __cnt)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>
rotr(_Tp __t,int __cnt)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