libcxx/include/__bits

   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