Marshall Clow | bf32ec9 | 2018-08-17 16:07:48 +0000 | [diff] [blame^] | 1 | // -*- C++ -*- |
| 2 | //===------------------------------ bit ----------------------------------===// |
| 3 | // |
| 4 | // The LLVM Compiler Infrastructure |
| 5 | // |
| 6 | // This file is dual licensed under the MIT and the University of Illinois Open |
| 7 | // Source Licenses. See LICENSE.TXT for details. |
| 8 | // |
| 9 | //===---------------------------------------------------------------------===// |
| 10 | |
| 11 | #ifndef _LIBCPP_BIT |
| 12 | #define _LIBCPP_BIT |
| 13 | |
| 14 | /* |
| 15 | bit synopsis |
| 16 | |
| 17 | namespace std { |
| 18 | |
| 19 | } // namespace std |
| 20 | |
| 21 | */ |
| 22 | |
| 23 | #include <__config> |
| 24 | |
| 25 | #if defined(__IBMCPP__) |
| 26 | #include "support/ibm/support.h" |
| 27 | #endif |
| 28 | #if defined(_LIBCPP_COMPILER_MSVC) |
| 29 | #include <intrin.h> |
| 30 | #endif |
| 31 | |
| 32 | #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| 33 | #pragma GCC system_header |
| 34 | #endif |
| 35 | |
| 36 | _LIBCPP_BEGIN_NAMESPACE_STD |
| 37 | |
| 38 | // Precondition: __x != 0 |
| 39 | inline _LIBCPP_INLINE_VISIBILITY |
| 40 | unsigned __ctz(unsigned __x) { |
| 41 | #ifndef _LIBCPP_COMPILER_MSVC |
| 42 | return static_cast<unsigned>(__builtin_ctz(__x)); |
| 43 | #else |
| 44 | static_assert(sizeof(unsigned) == sizeof(unsigned long), ""); |
| 45 | static_assert(sizeof(unsigned long) == 4, ""); |
| 46 | unsigned long where; |
| 47 | // Search from LSB to MSB for first set bit. |
| 48 | // Returns zero if no set bit is found. |
| 49 | if (_BitScanForward(&where, __x)) |
| 50 | return where; |
| 51 | return 32; |
| 52 | #endif |
| 53 | } |
| 54 | |
| 55 | inline _LIBCPP_INLINE_VISIBILITY |
| 56 | unsigned long __ctz(unsigned long __x) { |
| 57 | #ifndef _LIBCPP_COMPILER_MSVC |
| 58 | return static_cast<unsigned long>(__builtin_ctzl(__x)); |
| 59 | #else |
| 60 | static_assert(sizeof(unsigned long) == sizeof(unsigned), ""); |
| 61 | return __ctz(static_cast<unsigned>(__x)); |
| 62 | #endif |
| 63 | } |
| 64 | |
| 65 | inline _LIBCPP_INLINE_VISIBILITY |
| 66 | unsigned long long __ctz(unsigned long long __x) { |
| 67 | #ifndef _LIBCPP_COMPILER_MSVC |
| 68 | return static_cast<unsigned long long>(__builtin_ctzll(__x)); |
| 69 | #else |
| 70 | unsigned long where; |
| 71 | // Search from LSB to MSB for first set bit. |
| 72 | // Returns zero if no set bit is found. |
| 73 | #if defined(_LIBCPP_HAS_BITSCAN64) |
| 74 | (defined(_M_AMD64) || defined(__x86_64__)) |
| 75 | if (_BitScanForward64(&where, __x)) |
| 76 | return static_cast<int>(where); |
| 77 | #else |
| 78 | // Win32 doesn't have _BitScanForward64 so emulate it with two 32 bit calls. |
| 79 | // Scan the Low Word. |
| 80 | if (_BitScanForward(&where, static_cast<unsigned long>(__x))) |
| 81 | return where; |
| 82 | // Scan the High Word. |
| 83 | if (_BitScanForward(&where, static_cast<unsigned long>(__x >> 32))) |
| 84 | return where + 32; // Create a bit offset from the LSB. |
| 85 | #endif |
| 86 | return 64; |
| 87 | #endif // _LIBCPP_COMPILER_MSVC |
| 88 | } |
| 89 | |
| 90 | // Precondition: __x != 0 |
| 91 | inline _LIBCPP_INLINE_VISIBILITY |
| 92 | unsigned __clz(unsigned __x) { |
| 93 | #ifndef _LIBCPP_COMPILER_MSVC |
| 94 | return static_cast<unsigned>(__builtin_clz(__x)); |
| 95 | #else |
| 96 | static_assert(sizeof(unsigned) == sizeof(unsigned long), ""); |
| 97 | static_assert(sizeof(unsigned long) == 4, ""); |
| 98 | unsigned long where; |
| 99 | // Search from LSB to MSB for first set bit. |
| 100 | // Returns zero if no set bit is found. |
| 101 | if (_BitScanReverse(&where, __x)) |
| 102 | return 31 - where; |
| 103 | return 32; // Undefined Behavior. |
| 104 | #endif |
| 105 | } |
| 106 | |
| 107 | inline _LIBCPP_INLINE_VISIBILITY |
| 108 | unsigned long __clz(unsigned long __x) { |
| 109 | #ifndef _LIBCPP_COMPILER_MSVC |
| 110 | return static_cast<unsigned long>(__builtin_clzl (__x)); |
| 111 | #else |
| 112 | static_assert(sizeof(unsigned) == sizeof(unsigned long), ""); |
| 113 | return __clz(static_cast<unsigned>(__x)); |
| 114 | #endif |
| 115 | } |
| 116 | |
| 117 | inline _LIBCPP_INLINE_VISIBILITY |
| 118 | unsigned long long __clz(unsigned long long __x) { |
| 119 | #ifndef _LIBCPP_COMPILER_MSVC |
| 120 | return static_cast<unsigned long long>(__builtin_clzll(__x)); |
| 121 | #else |
| 122 | unsigned long where; |
| 123 | // BitScanReverse scans from MSB to LSB for first set bit. |
| 124 | // Returns 0 if no set bit is found. |
| 125 | #if defined(_LIBCPP_HAS_BITSCAN64) |
| 126 | if (_BitScanReverse64(&where, __x)) |
| 127 | return static_cast<int>(63 - where); |
| 128 | #else |
| 129 | // Scan the high 32 bits. |
| 130 | if (_BitScanReverse(&where, static_cast<unsigned long>(__x >> 32))) |
| 131 | return 63 - (where + 32); // Create a bit offset from the MSB. |
| 132 | // Scan the low 32 bits. |
| 133 | if (_BitScanReverse(&where, static_cast<unsigned long>(__x))) |
| 134 | return 63 - where; |
| 135 | #endif |
| 136 | return 64; // Undefined Behavior. |
| 137 | #endif // _LIBCPP_COMPILER_MSVC |
| 138 | } |
| 139 | |
| 140 | inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned __x) { |
| 141 | #ifndef _LIBCPP_COMPILER_MSVC |
| 142 | return __builtin_popcount (__x); |
| 143 | #else |
| 144 | static_assert(sizeof(unsigned) == 4, ""); |
| 145 | return __popcnt(__x); |
| 146 | #endif |
| 147 | } |
| 148 | |
| 149 | inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned long __x) { |
| 150 | #ifndef _LIBCPP_COMPILER_MSVC |
| 151 | return __builtin_popcountl (__x); |
| 152 | #else |
| 153 | static_assert(sizeof(unsigned long) == 4, ""); |
| 154 | return __popcnt(__x); |
| 155 | #endif |
| 156 | } |
| 157 | |
| 158 | inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned long long __x) { |
| 159 | #ifndef _LIBCPP_COMPILER_MSVC |
| 160 | return __builtin_popcountll(__x); |
| 161 | #else |
| 162 | static_assert(sizeof(unsigned long long) == 8, ""); |
| 163 | return __popcnt64(__x); |
| 164 | #endif |
| 165 | } |
| 166 | |
| 167 | _LIBCPP_END_NAMESPACE_STD |
| 168 | |
| 169 | #endif // _LIBCPP_BIT |