xref: /freebsd/contrib/llvm-project/libcxx/include/bit (revision f976241773df2260e6170317080761d1c5814fe5) 
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} // namespace std
46
47*/
48
49#include <__config>
50#include <limits>
51#include <type_traits>
52#include <version>
53#include <__debug>
54
55#if defined(__IBMCPP__)
56#include "support/ibm/support.h"
57#endif
58#if defined(_LIBCPP_COMPILER_MSVC)
59#include <intrin.h>
60#endif
61
62#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
63#pragma GCC system_header
64#endif
65
66_LIBCPP_PUSH_MACROS
67#include <__undef_macros>
68
69_LIBCPP_BEGIN_NAMESPACE_STD
70
71#ifndef _LIBCPP_COMPILER_MSVC
72
73inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
74int __libcpp_ctz(unsigned __x)           _NOEXCEPT { return __builtin_ctz(__x); }
75
76inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
77int __libcpp_ctz(unsigned long __x)      _NOEXCEPT { return __builtin_ctzl(__x); }
78
79inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
80int __libcpp_ctz(unsigned long long __x) _NOEXCEPT { return __builtin_ctzll(__x); }
81
82
83inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
84int __libcpp_clz(unsigned __x)           _NOEXCEPT { return __builtin_clz(__x); }
85
86inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
87int __libcpp_clz(unsigned long __x)      _NOEXCEPT { return __builtin_clzl(__x); }
88
89inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
90int __libcpp_clz(unsigned long long __x) _NOEXCEPT { return __builtin_clzll(__x); }
91
92
93inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
94int __libcpp_popcount(unsigned __x)           _NOEXCEPT { return __builtin_popcount(__x); }
95
96inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
97int __libcpp_popcount(unsigned long __x)      _NOEXCEPT { return __builtin_popcountl(__x); }
98
99inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
100int __libcpp_popcount(unsigned long long __x) _NOEXCEPT { return __builtin_popcountll(__x); }
101
102#else  // _LIBCPP_COMPILER_MSVC
103
104// Precondition:  __x != 0
105inline _LIBCPP_INLINE_VISIBILITY
106int __libcpp_ctz(unsigned __x) {
107  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
108  static_assert(sizeof(unsigned long) == 4, "");
109  unsigned long __where;
110  if (_BitScanForward(&__where, __x))
111    return static_cast<int>(__where);
112  return 32;
113}
114
115inline _LIBCPP_INLINE_VISIBILITY
116int __libcpp_ctz(unsigned long __x) {
117    static_assert(sizeof(unsigned long) == sizeof(unsigned), "");
118    return __ctz(static_cast<unsigned>(__x));
119}
120
121inline _LIBCPP_INLINE_VISIBILITY
122int __libcpp_ctz(unsigned long long __x) {
123    unsigned long __where;
124#if defined(_LIBCPP_HAS_BITSCAN64)
125    (defined(_M_AMD64) || defined(__x86_64__))
126  if (_BitScanForward64(&__where, __x))
127    return static_cast<int>(__where);
128#else
129  // Win32 doesn't have _BitScanForward64 so emulate it with two 32 bit calls.
130  if (_BitScanForward(&__where, static_cast<unsigned long>(__x)))
131    return static_cast<int>(__where);
132  if (_BitScanForward(&__where, static_cast<unsigned long>(__x >> 32)))
133    return static_cast<int>(__where + 32);
134#endif
135  return 64;
136}
137
138// Precondition:  __x != 0
139inline _LIBCPP_INLINE_VISIBILITY
140int __libcpp_clz(unsigned __x) {
141  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
142  static_assert(sizeof(unsigned long) == 4, "");
143  unsigned long __where;
144  if (_BitScanReverse(&__where, __x))
145    return static_cast<int>(31 - __where);
146  return 32; // Undefined Behavior.
147}
148
149inline _LIBCPP_INLINE_VISIBILITY
150int __libcpp_clz(unsigned long __x) {
151    static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
152    return __libcpp_clz(static_cast<unsigned>(__x));
153}
154
155inline _LIBCPP_INLINE_VISIBILITY
156int __libcpp_clz(unsigned long long __x) {
157  unsigned long __where;
158#if defined(_LIBCPP_HAS_BITSCAN64)
159  if (_BitScanReverse64(&__where, __x))
160    return static_cast<int>(63 - __where);
161#else
162  // Win32 doesn't have _BitScanReverse64 so emulate it with two 32 bit calls.
163  if (_BitScanReverse(&__where, static_cast<unsigned long>(__x >> 32)))
164    return static_cast<int>(63 - (__where + 32));
165  if (_BitScanReverse(&__where, static_cast<unsigned long>(__x)))
166    return static_cast<int>(63 - __where);
167#endif
168  return 64; // Undefined Behavior.
169}
170
171inline _LIBCPP_INLINE_VISIBILITY int __libcpp_popcount(unsigned __x) {
172  static_assert(sizeof(unsigned) == 4, "");
173  return __popcnt(__x);
174}
175
176inline _LIBCPP_INLINE_VISIBILITY int __libcpp_popcount(unsigned long __x) {
177  static_assert(sizeof(unsigned long) == 4, "");
178  return __popcnt(__x);
179}
180
181inline _LIBCPP_INLINE_VISIBILITY int __libcpp_popcount(unsigned long long __x) {
182  static_assert(sizeof(unsigned long long) == 8, "");
183  return __popcnt64(__x);
184}
185
186#endif // _LIBCPP_COMPILER_MSVC
187
188template <class _Tp>
189using __bitop_unsigned_integer _LIBCPP_NODEBUG_TYPE = integral_constant<bool,
190         is_integral<_Tp>::value &&
191         is_unsigned<_Tp>::value &&
192        _IsNotSame<typename remove_cv<_Tp>::type, bool>::value &&
193        _IsNotSame<typename remove_cv<_Tp>::type, signed char>::value &&
194        _IsNotSame<typename remove_cv<_Tp>::type, wchar_t>::value &&
195        _IsNotSame<typename remove_cv<_Tp>::type, char16_t>::value &&
196        _IsNotSame<typename remove_cv<_Tp>::type, char32_t>::value
197    >;
198
199
200template<class _Tp>
201_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
202_Tp __rotl(_Tp __t, unsigned int __cnt) _NOEXCEPT
203{
204    static_assert(__bitop_unsigned_integer<_Tp>::value, "__rotl requires unsigned");
205    const unsigned int __dig = numeric_limits<_Tp>::digits;
206    if ((__cnt % __dig) == 0)
207        return __t;
208    return (__t << (__cnt % __dig)) | (__t >> (__dig - (__cnt % __dig)));
209}
210
211
212template<class _Tp>
213_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
214_Tp __rotr(_Tp __t, unsigned int __cnt) _NOEXCEPT
215{
216    static_assert(__bitop_unsigned_integer<_Tp>::value, "__rotr requires unsigned");
217    const unsigned int __dig = numeric_limits<_Tp>::digits;
218    if ((__cnt % __dig) == 0)
219        return __t;
220    return (__t >> (__cnt % __dig)) | (__t << (__dig - (__cnt % __dig)));
221}
222
223
224
225template<class _Tp>
226_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
227int __countr_zero(_Tp __t) _NOEXCEPT
228{
229    static_assert(__bitop_unsigned_integer<_Tp>::value, "__countr_zero requires unsigned");
230    if (__t == 0)
231        return numeric_limits<_Tp>::digits;
232
233    if      (sizeof(_Tp) <= sizeof(unsigned int))
234        return __libcpp_ctz(static_cast<unsigned int>(__t));
235    else if (sizeof(_Tp) <= sizeof(unsigned long))
236        return __libcpp_ctz(static_cast<unsigned long>(__t));
237    else if (sizeof(_Tp) <= sizeof(unsigned long long))
238        return __libcpp_ctz(static_cast<unsigned long long>(__t));
239    else
240    {
241        int __ret = 0;
242        int __iter = 0;
243        const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
244        while ((__iter = __libcpp_ctz(static_cast<unsigned long long>(__t))) == __ulldigits)
245        {
246            __ret += __iter;
247            __t >>= __ulldigits;
248        }
249        return __ret + __iter;
250    }
251}
252
253template<class _Tp>
254_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
255int __countl_zero(_Tp __t) _NOEXCEPT
256{
257    static_assert(__bitop_unsigned_integer<_Tp>::value, "__countl_zero requires unsigned");
258    if (__t == 0)
259        return numeric_limits<_Tp>::digits;
260
261    if      (sizeof(_Tp) <= sizeof(unsigned int))
262        return __libcpp_clz(static_cast<unsigned int>(__t))
263              - (numeric_limits<unsigned int>::digits - numeric_limits<_Tp>::digits);
264    else if (sizeof(_Tp) <= sizeof(unsigned long))
265        return __libcpp_clz(static_cast<unsigned long>(__t))
266              - (numeric_limits<unsigned long>::digits - numeric_limits<_Tp>::digits);
267    else if (sizeof(_Tp) <= sizeof(unsigned long long))
268        return __libcpp_clz(static_cast<unsigned long long>(__t))
269              - (numeric_limits<unsigned long long>::digits - numeric_limits<_Tp>::digits);
270    else
271    {
272        int __ret = 0;
273        int __iter = 0;
274        const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
275        while (true) {
276            __t = __rotr(__t, __ulldigits);
277            if ((__iter = __countl_zero(static_cast<unsigned long long>(__t))) != __ulldigits)
278                break;
279            __ret += __iter;
280            }
281        return __ret + __iter;
282    }
283}
284
285template<class _Tp>
286_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
287int __countl_one(_Tp __t) _NOEXCEPT
288{
289    static_assert(__bitop_unsigned_integer<_Tp>::value, "__countl_one requires unsigned");
290    return __t != numeric_limits<_Tp>::max()
291        ? __countl_zero(static_cast<_Tp>(~__t))
292        : numeric_limits<_Tp>::digits;
293}
294
295
296template<class _Tp>
297_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
298int __countr_one(_Tp __t) _NOEXCEPT
299{
300    static_assert(__bitop_unsigned_integer<_Tp>::value, "__countr_one requires unsigned");
301    return __t != numeric_limits<_Tp>::max()
302        ? __countr_zero(static_cast<_Tp>(~__t))
303        : numeric_limits<_Tp>::digits;
304}
305
306
307template<class _Tp>
308_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
309int
310__popcount(_Tp __t) _NOEXCEPT
311{
312    static_assert(__bitop_unsigned_integer<_Tp>::value, "__libcpp_popcount requires unsigned");
313    if      (sizeof(_Tp) <= sizeof(unsigned int))
314        return __libcpp_popcount(static_cast<unsigned int>(__t));
315    else if (sizeof(_Tp) <= sizeof(unsigned long))
316        return __libcpp_popcount(static_cast<unsigned long>(__t));
317    else if (sizeof(_Tp) <= sizeof(unsigned long long))
318        return __libcpp_popcount(static_cast<unsigned long long>(__t));
319    else
320    {
321        int __ret = 0;
322        while (__t != 0)
323        {
324            __ret += __libcpp_popcount(static_cast<unsigned long long>(__t));
325            __t >>= numeric_limits<unsigned long long>::digits;
326        }
327        return __ret;
328    }
329}
330
331
332// integral log base 2
333template<class _Tp>
334_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
335unsigned __bit_log2(_Tp __t) _NOEXCEPT
336{
337    static_assert(__bitop_unsigned_integer<_Tp>::value, "__bit_log2 requires unsigned");
338    return std::numeric_limits<_Tp>::digits - 1 - __countl_zero(__t);
339}
340
341template <class _Tp>
342_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
343bool __ispow2(_Tp __t) _NOEXCEPT
344{
345    static_assert(__bitop_unsigned_integer<_Tp>::value, "__ispow2 requires unsigned");
346	return __t != 0 && (((__t & (__t - 1)) == 0));
347}
348
349
350#if _LIBCPP_STD_VER > 17
351
352template<class _Tp>
353_LIBCPP_INLINE_VISIBILITY constexpr
354enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
355rotl(_Tp __t, unsigned int __cnt) noexcept
356{
357    return __rotl(__t, __cnt);
358}
359
360
361// rotr
362template<class _Tp>
363_LIBCPP_INLINE_VISIBILITY constexpr
364enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
365rotr(_Tp __t, unsigned int __cnt) noexcept
366{
367    return __rotr(__t, __cnt);
368}
369
370
371template<class _Tp>
372_LIBCPP_INLINE_VISIBILITY constexpr
373enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
374countl_zero(_Tp __t) noexcept
375{
376    return __countl_zero(__t);
377}
378
379
380template<class _Tp>
381_LIBCPP_INLINE_VISIBILITY constexpr
382enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
383countl_one(_Tp __t) noexcept
384{
385    return __countl_one(__t);
386}
387
388
389template<class _Tp>
390_LIBCPP_INLINE_VISIBILITY constexpr
391enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
392countr_zero(_Tp __t) noexcept
393{
394	return __countr_zero(__t);
395}
396
397
398template<class _Tp>
399_LIBCPP_INLINE_VISIBILITY constexpr
400enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
401countr_one(_Tp __t) noexcept
402{
403    return __countr_one(__t);
404}
405
406
407template<class _Tp>
408_LIBCPP_INLINE_VISIBILITY constexpr
409enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
410popcount(_Tp __t) noexcept
411{
412    return __popcount(__t);
413}
414
415
416template <class _Tp>
417_LIBCPP_INLINE_VISIBILITY constexpr
418enable_if_t<__bitop_unsigned_integer<_Tp>::value, bool>
419ispow2(_Tp __t) noexcept
420{
421    return __ispow2(__t);
422}
423
424template <class _Tp>
425_LIBCPP_INLINE_VISIBILITY constexpr
426enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
427floor2(_Tp __t) noexcept
428{
429    return __t == 0 ? 0 : _Tp{1} << __bit_log2(__t);
430}
431
432template <class _Tp>
433_LIBCPP_INLINE_VISIBILITY constexpr
434enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
435ceil2(_Tp __t) noexcept
436{
437    if (__t < 2) return 1;
438    const unsigned __n = numeric_limits<_Tp>::digits - countl_zero((_Tp)(__t - 1u));
439    _LIBCPP_DEBUG_ASSERT(__libcpp_is_constant_evaluated() || __n != numeric_limits<_Tp>::digits, "Bad input to ceil2");
440
441    if constexpr (sizeof(_Tp) >= sizeof(unsigned))
442        return _Tp{1} << __n;
443    else
444    {
445        const unsigned __extra = numeric_limits<unsigned>::digits  - numeric_limits<_Tp>::digits;
446        const unsigned __retVal = 1u << (__n + __extra);
447        return (_Tp) (__retVal >> __extra);
448    }
449}
450
451template <class _Tp>
452_LIBCPP_INLINE_VISIBILITY constexpr
453enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
454log2p1(_Tp __t) noexcept
455{
456    return __t == 0 ? 0 : __bit_log2(__t) + 1;
457}
458
459#endif // _LIBCPP_STD_VER > 17
460
461_LIBCPP_END_NAMESPACE_STD
462
463_LIBCPP_POP_MACROS
464
465#endif // _LIBCPP_BIT
466