2 //===----------------------- support/win32/support.h ----------------------===//
4 // The LLVM Compiler Infrastructure
6 // This file is dual licensed under the MIT and the University of Illinois Open
7 // Source Licenses. See LICENSE.TXT for details.
9 //===----------------------------------------------------------------------===//
11 #ifndef _LIBCPP_SUPPORT_WIN32_SUPPORT_H
12 #define _LIBCPP_SUPPORT_WIN32_SUPPORT_H
14 // Functions and constants used in libc++ that
15 // are missing from the Windows C library.
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_MSVC)
24 #if defined(_LIBCPP_MSVCRT)
25 #include <crtversion.h>
27 #define swprintf _snwprintf
28 #define vswprintf _vsnwprintf
34 // The mingw headers already define these as static.
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);
47 #if defined(_VC_CRT_MAJOR_VERSION) && _VC_CRT_MAJOR_VERSION < 14
48 #define snprintf _snprintf
52 #if defined(_LIBCPP_MSVC)
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
57 static_assert(sizeof(unsigned long long) == 8, "");
58 static_assert(sizeof(unsigned long) == 4, "");
59 static_assert(sizeof(unsigned int) == 4, "");
61 _LIBCPP_ALWAYS_INLINE int __builtin_popcount(unsigned int x)
64 static const unsigned int m1 = 0x55555555;
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.
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;
81 _LIBCPP_ALWAYS_INLINE int __builtin_popcountl(unsigned long x)
83 return __builtin_popcount(static_cast<int>(x));
86 _LIBCPP_ALWAYS_INLINE int __builtin_popcountll(unsigned long long x)
89 static const unsigned long long m1 = 0x5555555555555555;
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.
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);
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)
111 // Search from LSB to MSB for first set bit.
112 // Returns zero if no set bit is found.
114 if (_BitScanForward64(&where, mask))
115 return static_cast<int>(where);
116 #elif defined(_WIN32)
117 // Win32 doesn't have _BitScanForward64 so emulate it with two 32 bit calls.
118 // Scan the Low Word.
119 if (_BitScanForward(&where, static_cast<unsigned long>(mask)))
120 return static_cast<int>(where);
121 // Scan the High Word.
122 if (_BitScanForward(&where, static_cast<unsigned long>(mask >> 32)))
123 return static_cast<int>(where + 32); // Create a bit offset from the LSB.
125 #error "Implementation of __builtin_ctzll required"
130 _LIBCPP_ALWAYS_INLINE int __builtin_ctzl(unsigned long mask)
133 // Search from LSB to MSB for first set bit.
134 // Returns zero if no set bit is found.
135 if (_BitScanForward(&where, mask))
136 return static_cast<int>(where);
140 _LIBCPP_ALWAYS_INLINE int __builtin_ctz(unsigned int mask)
142 // Win32 and Win64 expectations.
143 static_assert(sizeof(mask) == 4, "");
144 static_assert(sizeof(unsigned long) == 4, "");
145 return __builtin_ctzl(static_cast<unsigned long>(mask));
148 // Returns the number of leading 0-bits in x, starting at the most significant
149 // bit position. If x is 0, the result is undefined.
150 _LIBCPP_ALWAYS_INLINE int __builtin_clzll(unsigned long long mask)
153 // BitScanReverse scans from MSB to LSB for first set bit.
154 // Returns 0 if no set bit is found.
156 if (_BitScanReverse64(&where, mask))
157 return static_cast<int>(63 - where);
158 #elif defined(_WIN32)
159 // Scan the high 32 bits.
160 if (_BitScanReverse(&where, static_cast<unsigned long>(mask >> 32)))
161 return static_cast<int>(63 -
162 (where + 32)); // Create a bit offset from the MSB.
163 // Scan the low 32 bits.
164 if (_BitScanReverse(&where, static_cast<unsigned long>(mask)))
165 return static_cast<int>(63 - where);
167 #error "Implementation of __builtin_clzll required"
169 return 64; // Undefined Behavior.
172 _LIBCPP_ALWAYS_INLINE int __builtin_clzl(unsigned long mask)
175 // Search from LSB to MSB for first set bit.
176 // Returns zero if no set bit is found.
177 if (_BitScanReverse(&where, mask))
178 return static_cast<int>(31 - where);
179 return 32; // Undefined Behavior.
182 _LIBCPP_ALWAYS_INLINE int __builtin_clz(unsigned int x)
184 return __builtin_clzl(x);
186 #endif // _LIBCPP_MSVC
188 #endif // _LIBCPP_SUPPORT_WIN32_SUPPORT_H