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      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___BITS
     11 #define _LIBCPP___BITS
     12 
     13 #include <__config>
     14 
     15 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
     16 #pragma GCC system_header
     17 #endif
     18 
     19 _LIBCPP_PUSH_MACROS
     20 #include <__undef_macros>
     21 
     22 
     23 _LIBCPP_BEGIN_NAMESPACE_STD
     24 
     25 #ifndef _LIBCPP_COMPILER_MSVC
     26 
     27 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     28 int __libcpp_ctz(unsigned __x)           _NOEXCEPT { return __builtin_ctz(__x); }
     29 
     30 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     31 int __libcpp_ctz(unsigned long __x)      _NOEXCEPT { return __builtin_ctzl(__x); }
     32 
     33 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     34 int __libcpp_ctz(unsigned long long __x) _NOEXCEPT { return __builtin_ctzll(__x); }
     35 
     36 
     37 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     38 int __libcpp_clz(unsigned __x)           _NOEXCEPT { return __builtin_clz(__x); }
     39 
     40 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     41 int __libcpp_clz(unsigned long __x)      _NOEXCEPT { return __builtin_clzl(__x); }
     42 
     43 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     44 int __libcpp_clz(unsigned long long __x) _NOEXCEPT { return __builtin_clzll(__x); }
     45 
     46 
     47 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     48 int __libcpp_popcount(unsigned __x)           _NOEXCEPT { return __builtin_popcount(__x); }
     49 
     50 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     51 int __libcpp_popcount(unsigned long __x)      _NOEXCEPT { return __builtin_popcountl(__x); }
     52 
     53 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     54 int __libcpp_popcount(unsigned long long __x) _NOEXCEPT { return __builtin_popcountll(__x); }
     55 
     56 #else  // _LIBCPP_COMPILER_MSVC
     57 
     58 // Precondition:  __x != 0
     59 inline _LIBCPP_INLINE_VISIBILITY
     60 int __libcpp_ctz(unsigned __x) {
     61   static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
     62   static_assert(sizeof(unsigned long) == 4, "");
     63   unsigned long __where;
     64   if (_BitScanForward(&__where, __x))
     65     return static_cast<int>(__where);
     66   return 32;
     67 }
     68 
     69 inline _LIBCPP_INLINE_VISIBILITY
     70 int __libcpp_ctz(unsigned long __x) {
     71     static_assert(sizeof(unsigned long) == sizeof(unsigned), "");
     72     return __ctz(static_cast<unsigned>(__x));
     73 }
     74 
     75 inline _LIBCPP_INLINE_VISIBILITY
     76 int __libcpp_ctz(unsigned long long __x) {
     77     unsigned long __where;
     78 #if defined(_LIBCPP_HAS_BITSCAN64)
     79   if (_BitScanForward64(&__where, __x))
     80     return static_cast<int>(__where);
     81 #else
     82   // Win32 doesn't have _BitScanForward64 so emulate it with two 32 bit calls.
     83   if (_BitScanForward(&__where, static_cast<unsigned long>(__x)))
     84     return static_cast<int>(__where);
     85   if (_BitScanForward(&__where, static_cast<unsigned long>(__x >> 32)))
     86     return static_cast<int>(__where + 32);
     87 #endif
     88   return 64;
     89 }
     90 
     91 // Precondition:  __x != 0
     92 inline _LIBCPP_INLINE_VISIBILITY
     93 int __libcpp_clz(unsigned __x) {
     94   static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
     95   static_assert(sizeof(unsigned long) == 4, "");
     96   unsigned long __where;
     97   if (_BitScanReverse(&__where, __x))
     98     return static_cast<int>(31 - __where);
     99   return 32; // Undefined Behavior.
    100 }
    101 
    102 inline _LIBCPP_INLINE_VISIBILITY
    103 int __libcpp_clz(unsigned long __x) {
    104     static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
    105     return __libcpp_clz(static_cast<unsigned>(__x));
    106 }
    107 
    108 inline _LIBCPP_INLINE_VISIBILITY
    109 int __libcpp_clz(unsigned long long __x) {
    110   unsigned long __where;
    111 #if defined(_LIBCPP_HAS_BITSCAN64)
    112   if (_BitScanReverse64(&__where, __x))
    113     return static_cast<int>(63 - __where);
    114 #else
    115   // Win32 doesn't have _BitScanReverse64 so emulate it with two 32 bit calls.
    116   if (_BitScanReverse(&__where, static_cast<unsigned long>(__x >> 32)))
    117     return static_cast<int>(63 - (__where + 32));
    118   if (_BitScanReverse(&__where, static_cast<unsigned long>(__x)))
    119     return static_cast<int>(63 - __where);
    120 #endif
    121   return 64; // Undefined Behavior.
    122 }
    123 
    124 inline _LIBCPP_INLINE_VISIBILITY int __libcpp_popcount(unsigned __x) {
    125   static_assert(sizeof(unsigned) == 4, "");
    126   return __popcnt(__x);
    127 }
    128 
    129 inline _LIBCPP_INLINE_VISIBILITY int __libcpp_popcount(unsigned long __x) {
    130   static_assert(sizeof(unsigned long) == 4, "");
    131   return __popcnt(__x);
    132 }
    133 
    134 inline _LIBCPP_INLINE_VISIBILITY int __libcpp_popcount(unsigned long long __x) {
    135   static_assert(sizeof(unsigned long long) == 8, "");
    136   return __popcnt64(__x);
    137 }
    138 
    139 #endif // _LIBCPP_COMPILER_MSVC
    140 
    141 _LIBCPP_END_NAMESPACE_STD
    142 
    143 _LIBCPP_POP_MACROS
    144 
    145 #endif // _LIBCPP___BITS
    146