1 // -*- C++ -*- 2 //===----------------------- support/win32/support.h ----------------------===// 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_SUPPORT_WIN32_SUPPORT_H 12 #define _LIBCPP_SUPPORT_WIN32_SUPPORT_H 13 14 // Functions and constants used in libc++ that 15 // are missing from the Windows C library. 16 17 #include <wchar.h> // mbstate_t 18 #include <cstdarg> // va_ macros 19 // "builtins" not implemented here for Clang or GCC as they provide 20 // implementations. Assuming required for elsewhere else, certainly MSVC. 21 #if defined(_LIBCPP_COMPILER_MSVC) 22 #include <intrin.h> 23 #endif 24 #if defined(_LIBCPP_MSVCRT) 25 #include <crtversion.h> 26 #endif 27 #define swprintf _snwprintf 28 #define vswprintf _vsnwprintf 29 30 #ifndef NOMINMAX 31 #define NOMINMAX 32 #endif 33 34 // The mingw headers already define these as static. 35 #ifndef __MINGW32__ 36 extern "C" { 37 38 int vasprintf(char **sptr, const char *__restrict fmt, va_list ap); 39 int asprintf(char **sptr, const char *__restrict fmt, ...); 40 size_t mbsnrtowcs(wchar_t *__restrict dst, const char **__restrict src, 41 size_t nmc, size_t len, mbstate_t *__restrict ps); 42 size_t wcsnrtombs(char *__restrict dst, const wchar_t **__restrict src, 43 size_t nwc, size_t len, mbstate_t *__restrict ps); 44 } 45 #endif // __MINGW32__ 46 47 #if defined(_VC_CRT_MAJOR_VERSION) && _VC_CRT_MAJOR_VERSION < 14 48 #define snprintf _snprintf 49 #define _Exit _exit 50 #endif 51 52 #if defined(_LIBCPP_COMPILER_MSVC) 53 54 // Bit builtin's make these assumptions when calling _BitScanForward/Reverse 55 // etc. These assumptions are expected to be true for Win32/Win64 which this 56 // file supports. 57 static_assert(sizeof(unsigned long long) == 8, ""); 58 static_assert(sizeof(unsigned long) == 4, ""); 59 static_assert(sizeof(unsigned int) == 4, ""); 60 61 _LIBCPP_ALWAYS_INLINE int __builtin_popcount(unsigned int x) 62 { 63 // Binary: 0101... 64 static const unsigned int m1 = 0x55555555; 65 // Binary: 00110011.. 66 static const unsigned int m2 = 0x33333333; 67 // Binary: 4 zeros, 4 ones ... 68 static const unsigned int m4 = 0x0f0f0f0f; 69 // The sum of 256 to the power of 0,1,2,3... 70 static const unsigned int h01 = 0x01010101; 71 // Put count of each 2 bits into those 2 bits. 72 x -= (x >> 1) & m1; 73 // Put count of each 4 bits into those 4 bits. 74 x = (x & m2) + ((x >> 2) & m2); 75 // Put count of each 8 bits into those 8 bits. 76 x = (x + (x >> 4)) & m4; 77 // Returns left 8 bits of x + (x<<8) + (x<<16) + (x<<24). 78 return (x * h01) >> 24; 79 } 80 81 _LIBCPP_ALWAYS_INLINE int __builtin_popcountl(unsigned long x) 82 { 83 return __builtin_popcount(static_cast<int>(x)); 84 } 85 86 _LIBCPP_ALWAYS_INLINE int __builtin_popcountll(unsigned long long x) 87 { 88 // Binary: 0101... 89 static const unsigned long long m1 = 0x5555555555555555; 90 // Binary: 00110011.. 91 static const unsigned long long m2 = 0x3333333333333333; 92 // Binary: 4 zeros, 4 ones ... 93 static const unsigned long long m4 = 0x0f0f0f0f0f0f0f0f; 94 // The sum of 256 to the power of 0,1,2,3... 95 static const unsigned long long h01 = 0x0101010101010101; 96 // Put count of each 2 bits into those 2 bits. 97 x -= (x >> 1) & m1; 98 // Put count of each 4 bits into those 4 bits. 99 x = (x & m2) + ((x >> 2) & m2); 100 // Put count of each 8 bits into those 8 bits. 101 x = (x + (x >> 4)) & m4; 102 // Returns left 8 bits of x + (x<<8) + (x<<16) + (x<<24) + ... 103 return static_cast<int>((x * h01) >> 56); 104 } 105 106 // Returns the number of trailing 0-bits in x, starting at the least significant 107 // bit position. If x is 0, the result is undefined. 108 _LIBCPP_ALWAYS_INLINE int __builtin_ctzll(unsigned long long mask) 109 { 110 unsigned long where; 111 // Search from LSB to MSB for first set bit. 112 // Returns zero if no set bit is found. 113 #if defined(_LIBCPP_HAS_BITSCAN64) 114 (defined(_M_AMD64) || defined(__x86_64__)) 115 if (_BitScanForward64(&where, mask)) 116 return static_cast<int>(where); 117 #else 118 // Win32 doesn't have _BitScanForward64 so emulate it with two 32 bit calls. 119 // Scan the Low Word. 120 if (_BitScanForward(&where, static_cast<unsigned long>(mask))) 121 return static_cast<int>(where); 122 // Scan the High Word. 123 if (_BitScanForward(&where, static_cast<unsigned long>(mask >> 32))) 124 return static_cast<int>(where + 32); // Create a bit offset from the LSB. 125 #endif 126 return 64; 127 } 128 129 _LIBCPP_ALWAYS_INLINE int __builtin_ctzl(unsigned long mask) 130 { 131 unsigned long where; 132 // Search from LSB to MSB for first set bit. 133 // Returns zero if no set bit is found. 134 if (_BitScanForward(&where, mask)) 135 return static_cast<int>(where); 136 return 32; 137 } 138 139 _LIBCPP_ALWAYS_INLINE int __builtin_ctz(unsigned int mask) 140 { 141 // Win32 and Win64 expectations. 142 static_assert(sizeof(mask) == 4, ""); 143 static_assert(sizeof(unsigned long) == 4, ""); 144 return __builtin_ctzl(static_cast<unsigned long>(mask)); 145 } 146 147 // Returns the number of leading 0-bits in x, starting at the most significant 148 // bit position. If x is 0, the result is undefined. 149 _LIBCPP_ALWAYS_INLINE int __builtin_clzll(unsigned long long mask) 150 { 151 unsigned long where; 152 // BitScanReverse scans from MSB to LSB for first set bit. 153 // Returns 0 if no set bit is found. 154 #if defined(_LIBCPP_HAS_BITSCAN64) 155 if (_BitScanReverse64(&where, mask)) 156 return static_cast<int>(63 - where); 157 #else 158 // Scan the high 32 bits. 159 if (_BitScanReverse(&where, static_cast<unsigned long>(mask >> 32))) 160 return static_cast<int>(63 - 161 (where + 32)); // Create a bit offset from the MSB. 162 // Scan the low 32 bits. 163 if (_BitScanReverse(&where, static_cast<unsigned long>(mask))) 164 return static_cast<int>(63 - where); 165 #endif 166 return 64; // Undefined Behavior. 167 } 168 169 _LIBCPP_ALWAYS_INLINE int __builtin_clzl(unsigned long mask) 170 { 171 unsigned long where; 172 // Search from LSB to MSB for first set bit. 173 // Returns zero if no set bit is found. 174 if (_BitScanReverse(&where, mask)) 175 return static_cast<int>(31 - where); 176 return 32; // Undefined Behavior. 177 } 178 179 _LIBCPP_ALWAYS_INLINE int __builtin_clz(unsigned int x) 180 { 181 return __builtin_clzl(x); 182 } 183 #endif // _LIBCPP_MSVC 184 185 #endif // _LIBCPP_SUPPORT_WIN32_SUPPORT_H 186
