xref: /freebsd/contrib/llvm-project/libcxx/include/bit (revision 85868e8a1daeaae7a0e48effb2ea2310ae3b02c6) 
1// -*- C++ -*-
2//===------------------------------ bit ----------------------------------===//
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
18  template <class T>
19    constexpr bool ispow2(T x) noexcept; // C++20
20  template <class T>
21    constexpr T ceil2(T x);              // C++20
22  template <class T>
23    constexpr T floor2(T x) noexcept;    // C++20
24  template <class T>
25    constexpr T log2p1(T x) noexcept;    // C++20
26
27  // 23.20.2, rotating
28  template<class T>
29    constexpr T rotl(T x, unsigned int s) noexcept; // C++20
30  template<class T>
31    constexpr T rotr(T x, unsigned int s) noexcept; // C++20
32
33  // 23.20.3, counting
34  template<class T>
35    constexpr int countl_zero(T x) noexcept;  // C++20
36  template<class T>
37    constexpr int countl_one(T x) noexcept;   // C++20
38  template<class T>
39    constexpr int countr_zero(T x) noexcept;  // C++20
40  template<class T>
41    constexpr int countr_one(T x) noexcept;   // C++20
42  template<class T>
43    constexpr int popcount(T x) noexcept;     // C++20
44
45  // 20.15.9, endian
46  enum class endian {
47    little = see below,        // C++20
48    big = see below,           // C++20
49    native = see below         // C++20
50};
51
52} // namespace std
53
54*/
55
56#include <__config>
57#include <limits>
58#include <type_traits>
59#include <version>
60#include <__debug>
61
62#if defined(__IBMCPP__)
63#include "support/ibm/support.h"
64#endif
65#if defined(_LIBCPP_COMPILER_MSVC)
66#include <intrin.h>
67#endif
68
69#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
70#pragma GCC system_header
71#endif
72
73_LIBCPP_PUSH_MACROS
74#include <__undef_macros>
75
76_LIBCPP_BEGIN_NAMESPACE_STD
77
78#ifndef _LIBCPP_COMPILER_MSVC
79
80inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
81int __libcpp_ctz(unsigned __x)           _NOEXCEPT { return __builtin_ctz(__x); }
82
83inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
84int __libcpp_ctz(unsigned long __x)      _NOEXCEPT { return __builtin_ctzl(__x); }
85
86inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
87int __libcpp_ctz(unsigned long long __x) _NOEXCEPT { return __builtin_ctzll(__x); }
88
89
90inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
91int __libcpp_clz(unsigned __x)           _NOEXCEPT { return __builtin_clz(__x); }
92
93inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
94int __libcpp_clz(unsigned long __x)      _NOEXCEPT { return __builtin_clzl(__x); }
95
96inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
97int __libcpp_clz(unsigned long long __x) _NOEXCEPT { return __builtin_clzll(__x); }
98
99
100inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
101int __libcpp_popcount(unsigned __x)           _NOEXCEPT { return __builtin_popcount(__x); }
102
103inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
104int __libcpp_popcount(unsigned long __x)      _NOEXCEPT { return __builtin_popcountl(__x); }
105
106inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
107int __libcpp_popcount(unsigned long long __x) _NOEXCEPT { return __builtin_popcountll(__x); }
108
109#else  // _LIBCPP_COMPILER_MSVC
110
111// Precondition:  __x != 0
112inline _LIBCPP_INLINE_VISIBILITY
113int __libcpp_ctz(unsigned __x) {
114  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
115  static_assert(sizeof(unsigned long) == 4, "");
116  unsigned long __where;
117  if (_BitScanForward(&__where, __x))
118    return static_cast<int>(__where);
119  return 32;
120}
121
122inline _LIBCPP_INLINE_VISIBILITY
123int __libcpp_ctz(unsigned long __x) {
124    static_assert(sizeof(unsigned long) == sizeof(unsigned), "");
125    return __ctz(static_cast<unsigned>(__x));
126}
127
128inline _LIBCPP_INLINE_VISIBILITY
129int __libcpp_ctz(unsigned long long __x) {
130    unsigned long __where;
131#if defined(_LIBCPP_HAS_BITSCAN64)
132    (defined(_M_AMD64) || defined(__x86_64__))
133  if (_BitScanForward64(&__where, __x))
134    return static_cast<int>(__where);
135#else
136  // Win32 doesn't have _BitScanForward64 so emulate it with two 32 bit calls.
137  if (_BitScanForward(&__where, static_cast<unsigned long>(__x)))
138    return static_cast<int>(__where);
139  if (_BitScanForward(&__where, static_cast<unsigned long>(__x >> 32)))
140    return static_cast<int>(__where + 32);
141#endif
142  return 64;
143}
144
145// Precondition:  __x != 0
146inline _LIBCPP_INLINE_VISIBILITY
147int __libcpp_clz(unsigned __x) {
148  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
149  static_assert(sizeof(unsigned long) == 4, "");
150  unsigned long __where;
151  if (_BitScanReverse(&__where, __x))
152    return static_cast<int>(31 - __where);
153  return 32; // Undefined Behavior.
154}
155
156inline _LIBCPP_INLINE_VISIBILITY
157int __libcpp_clz(unsigned long __x) {
158    static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
159    return __libcpp_clz(static_cast<unsigned>(__x));
160}
161
162inline _LIBCPP_INLINE_VISIBILITY
163int __libcpp_clz(unsigned long long __x) {
164  unsigned long __where;
165#if defined(_LIBCPP_HAS_BITSCAN64)
166  if (_BitScanReverse64(&__where, __x))
167    return static_cast<int>(63 - __where);
168#else
169  // Win32 doesn't have _BitScanReverse64 so emulate it with two 32 bit calls.
170  if (_BitScanReverse(&__where, static_cast<unsigned long>(__x >> 32)))
171    return static_cast<int>(63 - (__where + 32));
172  if (_BitScanReverse(&__where, static_cast<unsigned long>(__x)))
173    return static_cast<int>(63 - __where);
174#endif
175  return 64; // Undefined Behavior.
176}
177
178inline _LIBCPP_INLINE_VISIBILITY int __libcpp_popcount(unsigned __x) {
179  static_assert(sizeof(unsigned) == 4, "");
180  return __popcnt(__x);
181}
182
183inline _LIBCPP_INLINE_VISIBILITY int __libcpp_popcount(unsigned long __x) {
184  static_assert(sizeof(unsigned long) == 4, "");
185  return __popcnt(__x);
186}
187
188inline _LIBCPP_INLINE_VISIBILITY int __libcpp_popcount(unsigned long long __x) {
189  static_assert(sizeof(unsigned long long) == 8, "");
190  return __popcnt64(__x);
191}
192
193#endif // _LIBCPP_COMPILER_MSVC
194
195template <class _Tp>
196using __bitop_unsigned_integer _LIBCPP_NODEBUG_TYPE = integral_constant<bool,
197         is_integral<_Tp>::value &&
198         is_unsigned<_Tp>::value &&
199        _IsNotSame<typename remove_cv<_Tp>::type, bool>::value &&
200        _IsNotSame<typename remove_cv<_Tp>::type, signed char>::value &&
201        _IsNotSame<typename remove_cv<_Tp>::type, wchar_t>::value &&
202        _IsNotSame<typename remove_cv<_Tp>::type, char16_t>::value &&
203        _IsNotSame<typename remove_cv<_Tp>::type, char32_t>::value
204    >;
205
206
207template<class _Tp>
208_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
209_Tp __rotl(_Tp __t, unsigned int __cnt) _NOEXCEPT
210{
211    static_assert(__bitop_unsigned_integer<_Tp>::value, "__rotl requires unsigned");
212    const unsigned int __dig = numeric_limits<_Tp>::digits;
213    if ((__cnt % __dig) == 0)
214        return __t;
215    return (__t << (__cnt % __dig)) | (__t >> (__dig - (__cnt % __dig)));
216}
217
218
219template<class _Tp>
220_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
221_Tp __rotr(_Tp __t, unsigned int __cnt) _NOEXCEPT
222{
223    static_assert(__bitop_unsigned_integer<_Tp>::value, "__rotr requires unsigned");
224    const unsigned int __dig = numeric_limits<_Tp>::digits;
225    if ((__cnt % __dig) == 0)
226        return __t;
227    return (__t >> (__cnt % __dig)) | (__t << (__dig - (__cnt % __dig)));
228}
229
230
231
232template<class _Tp>
233_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
234int __countr_zero(_Tp __t) _NOEXCEPT
235{
236    static_assert(__bitop_unsigned_integer<_Tp>::value, "__countr_zero requires unsigned");
237    if (__t == 0)
238        return numeric_limits<_Tp>::digits;
239
240    if      (sizeof(_Tp) <= sizeof(unsigned int))
241        return __libcpp_ctz(static_cast<unsigned int>(__t));
242    else if (sizeof(_Tp) <= sizeof(unsigned long))
243        return __libcpp_ctz(static_cast<unsigned long>(__t));
244    else if (sizeof(_Tp) <= sizeof(unsigned long long))
245        return __libcpp_ctz(static_cast<unsigned long long>(__t));
246    else
247    {
248        int __ret = 0;
249        int __iter = 0;
250        const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
251        while ((__iter = __libcpp_ctz(static_cast<unsigned long long>(__t))) == __ulldigits)
252        {
253            __ret += __iter;
254            __t >>= __ulldigits;
255        }
256        return __ret + __iter;
257    }
258}
259
260template<class _Tp>
261_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
262int __countl_zero(_Tp __t) _NOEXCEPT
263{
264    static_assert(__bitop_unsigned_integer<_Tp>::value, "__countl_zero requires unsigned");
265    if (__t == 0)
266        return numeric_limits<_Tp>::digits;
267
268    if      (sizeof(_Tp) <= sizeof(unsigned int))
269        return __libcpp_clz(static_cast<unsigned int>(__t))
270              - (numeric_limits<unsigned int>::digits - numeric_limits<_Tp>::digits);
271    else if (sizeof(_Tp) <= sizeof(unsigned long))
272        return __libcpp_clz(static_cast<unsigned long>(__t))
273              - (numeric_limits<unsigned long>::digits - numeric_limits<_Tp>::digits);
274    else if (sizeof(_Tp) <= sizeof(unsigned long long))
275        return __libcpp_clz(static_cast<unsigned long long>(__t))
276              - (numeric_limits<unsigned long long>::digits - numeric_limits<_Tp>::digits);
277    else
278    {
279        int __ret = 0;
280        int __iter = 0;
281        const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
282        while (true) {
283            __t = __rotr(__t, __ulldigits);
284            if ((__iter = __countl_zero(static_cast<unsigned long long>(__t))) != __ulldigits)
285                break;
286            __ret += __iter;
287            }
288        return __ret + __iter;
289    }
290}
291
292template<class _Tp>
293_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
294int __countl_one(_Tp __t) _NOEXCEPT
295{
296    static_assert(__bitop_unsigned_integer<_Tp>::value, "__countl_one requires unsigned");
297    return __t != numeric_limits<_Tp>::max()
298        ? __countl_zero(static_cast<_Tp>(~__t))
299        : numeric_limits<_Tp>::digits;
300}
301
302
303template<class _Tp>
304_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
305int __countr_one(_Tp __t) _NOEXCEPT
306{
307    static_assert(__bitop_unsigned_integer<_Tp>::value, "__countr_one requires unsigned");
308    return __t != numeric_limits<_Tp>::max()
309        ? __countr_zero(static_cast<_Tp>(~__t))
310        : numeric_limits<_Tp>::digits;
311}
312
313
314template<class _Tp>
315_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
316int
317__popcount(_Tp __t) _NOEXCEPT
318{
319    static_assert(__bitop_unsigned_integer<_Tp>::value, "__libcpp_popcount requires unsigned");
320    if      (sizeof(_Tp) <= sizeof(unsigned int))
321        return __libcpp_popcount(static_cast<unsigned int>(__t));
322    else if (sizeof(_Tp) <= sizeof(unsigned long))
323        return __libcpp_popcount(static_cast<unsigned long>(__t));
324    else if (sizeof(_Tp) <= sizeof(unsigned long long))
325        return __libcpp_popcount(static_cast<unsigned long long>(__t));
326    else
327    {
328        int __ret = 0;
329        while (__t != 0)
330        {
331            __ret += __libcpp_popcount(static_cast<unsigned long long>(__t));
332            __t >>= numeric_limits<unsigned long long>::digits;
333        }
334        return __ret;
335    }
336}
337
338
339// integral log base 2
340template<class _Tp>
341_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
342unsigned __bit_log2(_Tp __t) _NOEXCEPT
343{
344    static_assert(__bitop_unsigned_integer<_Tp>::value, "__bit_log2 requires unsigned");
345    return std::numeric_limits<_Tp>::digits - 1 - __countl_zero(__t);
346}
347
348template <class _Tp>
349_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
350bool __ispow2(_Tp __t) _NOEXCEPT
351{
352    static_assert(__bitop_unsigned_integer<_Tp>::value, "__ispow2 requires unsigned");
353	return __t != 0 && (((__t & (__t - 1)) == 0));
354}
355
356
357#if _LIBCPP_STD_VER > 17
358
359template<class _Tp>
360_LIBCPP_INLINE_VISIBILITY constexpr
361enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
362rotl(_Tp __t, unsigned int __cnt) noexcept
363{
364    return __rotl(__t, __cnt);
365}
366
367
368// rotr
369template<class _Tp>
370_LIBCPP_INLINE_VISIBILITY constexpr
371enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
372rotr(_Tp __t, unsigned int __cnt) noexcept
373{
374    return __rotr(__t, __cnt);
375}
376
377
378template<class _Tp>
379_LIBCPP_INLINE_VISIBILITY constexpr
380enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
381countl_zero(_Tp __t) noexcept
382{
383    return __countl_zero(__t);
384}
385
386
387template<class _Tp>
388_LIBCPP_INLINE_VISIBILITY constexpr
389enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
390countl_one(_Tp __t) noexcept
391{
392    return __countl_one(__t);
393}
394
395
396template<class _Tp>
397_LIBCPP_INLINE_VISIBILITY constexpr
398enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
399countr_zero(_Tp __t) noexcept
400{
401	return __countr_zero(__t);
402}
403
404
405template<class _Tp>
406_LIBCPP_INLINE_VISIBILITY constexpr
407enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
408countr_one(_Tp __t) noexcept
409{
410    return __countr_one(__t);
411}
412
413
414template<class _Tp>
415_LIBCPP_INLINE_VISIBILITY constexpr
416enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
417popcount(_Tp __t) noexcept
418{
419    return __popcount(__t);
420}
421
422
423template <class _Tp>
424_LIBCPP_INLINE_VISIBILITY constexpr
425enable_if_t<__bitop_unsigned_integer<_Tp>::value, bool>
426ispow2(_Tp __t) noexcept
427{
428    return __ispow2(__t);
429}
430
431template <class _Tp>
432_LIBCPP_INLINE_VISIBILITY constexpr
433enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
434floor2(_Tp __t) noexcept
435{
436    return __t == 0 ? 0 : _Tp{1} << __bit_log2(__t);
437}
438
439template <class _Tp>
440_LIBCPP_INLINE_VISIBILITY constexpr
441enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
442ceil2(_Tp __t) noexcept
443{
444    if (__t < 2) return 1;
445    const unsigned __n = numeric_limits<_Tp>::digits - countl_zero((_Tp)(__t - 1u));
446    _LIBCPP_DEBUG_ASSERT(__libcpp_is_constant_evaluated() || __n != numeric_limits<_Tp>::digits, "Bad input to ceil2");
447
448    if constexpr (sizeof(_Tp) >= sizeof(unsigned))
449        return _Tp{1} << __n;
450    else
451    {
452        const unsigned __extra = numeric_limits<unsigned>::digits  - numeric_limits<_Tp>::digits;
453        const unsigned __retVal = 1u << (__n + __extra);
454        return (_Tp) (__retVal >> __extra);
455    }
456}
457
458template <class _Tp>
459_LIBCPP_INLINE_VISIBILITY constexpr
460enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
461log2p1(_Tp __t) noexcept
462{
463    return __t == 0 ? 0 : __bit_log2(__t) + 1;
464}
465
466
467enum class endian
468{
469    little = 0xDEAD,
470    big    = 0xFACE,
471#if defined(_LIBCPP_LITTLE_ENDIAN)
472    native = little
473#elif defined(_LIBCPP_BIG_ENDIAN)
474    native = big
475#else
476    native = 0xCAFE
477#endif
478};
479
480#endif // _LIBCPP_STD_VER > 17
481
482_LIBCPP_END_NAMESPACE_STD
483
484_LIBCPP_POP_MACROS
485
486#endif // _LIBCPP_BIT
487