xref: /freebsd/contrib/llvm-project/libcxx/include/bit (revision a2464ee12761660f50d0b6f59f233949ebcacc87) 
1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===---------------------------------------------------------------------===//
9
10#ifndef _LIBCPP_BIT
11#define _LIBCPP_BIT
12
13/*
14    bit synopsis
15
16namespace std {
17  // [bit.cast], bit_cast
18  template<class To, class From>
19    constexpr To bit_cast(const From& from) noexcept; // C++20
20
21  // [bit.byteswap], byteswap
22  template<class T>
23    constexpr T byteswap(T value) noexcept;      // C++23
24
25  // [bit.pow.two], integral powers of 2
26  template <class T>
27    constexpr bool has_single_bit(T x) noexcept; // C++20
28  template <class T>
29    constexpr T bit_ceil(T x);                   // C++20
30  template <class T>
31    constexpr T bit_floor(T x) noexcept;         // C++20
32  template <class T>
33    constexpr T bit_width(T x) noexcept;         // C++20
34
35  // [bit.rotate], rotating
36  template<class T>
37    constexpr T rotl(T x, unsigned int s) noexcept; // C++20
38  template<class T>
39    constexpr T rotr(T x, unsigned int s) noexcept; // C++20
40
41  // [bit.count], counting
42  template<class T>
43    constexpr int countl_zero(T x) noexcept;  // C++20
44  template<class T>
45    constexpr int countl_one(T x) noexcept;   // C++20
46  template<class T>
47    constexpr int countr_zero(T x) noexcept;  // C++20
48  template<class T>
49    constexpr int countr_one(T x) noexcept;   // C++20
50  template<class T>
51    constexpr int popcount(T x) noexcept;     // C++20
52
53  // [bit.endian], endian
54  enum class endian {
55    little = see below,        // C++20
56    big = see below,           // C++20
57    native = see below         // C++20
58  };
59
60} // namespace std
61
62*/
63
64#include <__bit/bit_cast.h>
65#include <__bit/byteswap.h>
66#include <__bits> // __libcpp_clz
67#include <__config>
68#include <__debug>
69#include <limits>
70#include <type_traits>
71#include <version>
72
73#if defined(__IBMCPP__)
74#include "__support/ibm/support.h"
75#endif
76#if defined(_LIBCPP_COMPILER_MSVC)
77#include <intrin.h>
78#endif
79
80#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
81#pragma GCC system_header
82#endif
83
84_LIBCPP_PUSH_MACROS
85#include <__undef_macros>
86
87_LIBCPP_BEGIN_NAMESPACE_STD
88
89template<class _Tp>
90_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
91_Tp __rotl(_Tp __t, unsigned int __cnt) _NOEXCEPT
92{
93    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__rotl requires an unsigned integer type");
94    const unsigned int __dig = numeric_limits<_Tp>::digits;
95    if ((__cnt % __dig) == 0)
96        return __t;
97    return (__t << (__cnt % __dig)) | (__t >> (__dig - (__cnt % __dig)));
98}
99
100template<class _Tp>
101_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
102_Tp __rotr(_Tp __t, unsigned int __cnt) _NOEXCEPT
103{
104    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__rotr requires an unsigned integer type");
105    const unsigned int __dig = numeric_limits<_Tp>::digits;
106    if ((__cnt % __dig) == 0)
107        return __t;
108    return (__t >> (__cnt % __dig)) | (__t << (__dig - (__cnt % __dig)));
109}
110
111template<class _Tp>
112_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
113int __countr_zero(_Tp __t) _NOEXCEPT
114{
115    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__countr_zero requires an unsigned integer type");
116    if (__t == 0)
117        return numeric_limits<_Tp>::digits;
118
119    if      (sizeof(_Tp) <= sizeof(unsigned int))
120        return __libcpp_ctz(static_cast<unsigned int>(__t));
121    else if (sizeof(_Tp) <= sizeof(unsigned long))
122        return __libcpp_ctz(static_cast<unsigned long>(__t));
123    else if (sizeof(_Tp) <= sizeof(unsigned long long))
124        return __libcpp_ctz(static_cast<unsigned long long>(__t));
125    else
126    {
127        int __ret = 0;
128        const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
129        while (static_cast<unsigned long long>(__t) == 0uLL)
130        {
131            __ret += __ulldigits;
132            __t >>= __ulldigits;
133        }
134        return __ret + __libcpp_ctz(static_cast<unsigned long long>(__t));
135    }
136}
137
138template<class _Tp>
139_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
140int __countl_zero(_Tp __t) _NOEXCEPT
141{
142    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__countl_zero requires an unsigned integer type");
143    if (__t == 0)
144        return numeric_limits<_Tp>::digits;
145
146    if      (sizeof(_Tp) <= sizeof(unsigned int))
147        return __libcpp_clz(static_cast<unsigned int>(__t))
148              - (numeric_limits<unsigned int>::digits - numeric_limits<_Tp>::digits);
149    else if (sizeof(_Tp) <= sizeof(unsigned long))
150        return __libcpp_clz(static_cast<unsigned long>(__t))
151              - (numeric_limits<unsigned long>::digits - numeric_limits<_Tp>::digits);
152    else if (sizeof(_Tp) <= sizeof(unsigned long long))
153        return __libcpp_clz(static_cast<unsigned long long>(__t))
154              - (numeric_limits<unsigned long long>::digits - numeric_limits<_Tp>::digits);
155    else
156    {
157        int __ret = 0;
158        int __iter = 0;
159        const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
160        while (true) {
161            __t = __rotr(__t, __ulldigits);
162            if ((__iter = __countl_zero(static_cast<unsigned long long>(__t))) != __ulldigits)
163                break;
164            __ret += __iter;
165            }
166        return __ret + __iter;
167    }
168}
169
170template<class _Tp>
171_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
172int __countl_one(_Tp __t) _NOEXCEPT
173{
174    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__countl_one requires an unsigned integer type");
175    return __t != numeric_limits<_Tp>::max()
176        ? __countl_zero(static_cast<_Tp>(~__t))
177        : numeric_limits<_Tp>::digits;
178}
179
180template<class _Tp>
181_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
182int __countr_one(_Tp __t) _NOEXCEPT
183{
184    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__countr_one requires an unsigned integer type");
185    return __t != numeric_limits<_Tp>::max()
186        ? __countr_zero(static_cast<_Tp>(~__t))
187        : numeric_limits<_Tp>::digits;
188}
189
190template<class _Tp>
191_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
192int __popcount(_Tp __t) _NOEXCEPT
193{
194    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__popcount requires an unsigned integer type");
195    if      (sizeof(_Tp) <= sizeof(unsigned int))
196        return __libcpp_popcount(static_cast<unsigned int>(__t));
197    else if (sizeof(_Tp) <= sizeof(unsigned long))
198        return __libcpp_popcount(static_cast<unsigned long>(__t));
199    else if (sizeof(_Tp) <= sizeof(unsigned long long))
200        return __libcpp_popcount(static_cast<unsigned long long>(__t));
201    else
202    {
203        int __ret = 0;
204        while (__t != 0)
205        {
206            __ret += __libcpp_popcount(static_cast<unsigned long long>(__t));
207            __t >>= numeric_limits<unsigned long long>::digits;
208        }
209        return __ret;
210    }
211}
212
213// integral log base 2
214template<class _Tp>
215_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
216unsigned __bit_log2(_Tp __t) _NOEXCEPT
217{
218    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__bit_log2 requires an unsigned integer type");
219    return numeric_limits<_Tp>::digits - 1 - __countl_zero(__t);
220}
221
222template <class _Tp>
223_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
224bool __has_single_bit(_Tp __t) _NOEXCEPT
225{
226    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__has_single_bit requires an unsigned integer type");
227    return __t != 0 && (((__t & (__t - 1)) == 0));
228}
229
230#if _LIBCPP_STD_VER > 17
231
232template<class _Tp>
233_LIBCPP_INLINE_VISIBILITY constexpr
234enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, _Tp>
235rotl(_Tp __t, unsigned int __cnt) noexcept
236{
237    return __rotl(__t, __cnt);
238}
239
240template<class _Tp>
241_LIBCPP_INLINE_VISIBILITY constexpr
242enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, _Tp>
243rotr(_Tp __t, unsigned int __cnt) noexcept
244{
245    return __rotr(__t, __cnt);
246}
247
248template<class _Tp>
249_LIBCPP_INLINE_VISIBILITY constexpr
250enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, int>
251countl_zero(_Tp __t) noexcept
252{
253    return __countl_zero(__t);
254}
255
256template<class _Tp>
257_LIBCPP_INLINE_VISIBILITY constexpr
258enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, int>
259countl_one(_Tp __t) noexcept
260{
261    return __countl_one(__t);
262}
263
264template<class _Tp>
265_LIBCPP_INLINE_VISIBILITY constexpr
266enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, int>
267countr_zero(_Tp __t) noexcept
268{
269    return __countr_zero(__t);
270}
271
272template<class _Tp>
273_LIBCPP_INLINE_VISIBILITY constexpr
274enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, int>
275countr_one(_Tp __t) noexcept
276{
277    return __countr_one(__t);
278}
279
280template<class _Tp>
281_LIBCPP_INLINE_VISIBILITY constexpr
282enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, int>
283popcount(_Tp __t) noexcept
284{
285    return __popcount(__t);
286}
287
288template <class _Tp>
289_LIBCPP_INLINE_VISIBILITY constexpr
290enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, bool>
291has_single_bit(_Tp __t) noexcept
292{
293    return __has_single_bit(__t);
294}
295
296template <class _Tp>
297_LIBCPP_INLINE_VISIBILITY constexpr
298enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, _Tp>
299bit_floor(_Tp __t) noexcept
300{
301    return __t == 0 ? 0 : _Tp{1} << __bit_log2(__t);
302}
303
304template <class _Tp>
305_LIBCPP_INLINE_VISIBILITY constexpr
306enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, _Tp>
307bit_ceil(_Tp __t) noexcept
308{
309    if (__t < 2) return 1;
310    const unsigned __n = numeric_limits<_Tp>::digits - countl_zero((_Tp)(__t - 1u));
311    _LIBCPP_ASSERT(__n != numeric_limits<_Tp>::digits, "Bad input to bit_ceil");
312
313    if constexpr (sizeof(_Tp) >= sizeof(unsigned))
314        return _Tp{1} << __n;
315    else
316    {
317        const unsigned __extra = numeric_limits<unsigned>::digits  - numeric_limits<_Tp>::digits;
318        const unsigned __retVal = 1u << (__n + __extra);
319        return (_Tp) (__retVal >> __extra);
320    }
321}
322
323template <class _Tp>
324_LIBCPP_INLINE_VISIBILITY constexpr
325enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, _Tp>
326bit_width(_Tp __t) noexcept
327{
328    return __t == 0 ? 0 : __bit_log2(__t) + 1;
329}
330
331enum class endian
332{
333    little = 0xDEAD,
334    big    = 0xFACE,
335#if defined(_LIBCPP_LITTLE_ENDIAN)
336    native = little
337#elif defined(_LIBCPP_BIG_ENDIAN)
338    native = big
339#else
340    native = 0xCAFE
341#endif
342};
343
344#endif // _LIBCPP_STD_VER > 17
345
346_LIBCPP_END_NAMESPACE_STD
347
348_LIBCPP_POP_MACROS
349
350#endif // _LIBCPP_BIT
351