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 27inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 28int __libcpp_ctz(unsigned __x) _NOEXCEPT { return __builtin_ctz(__x); } 29 30inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 31int __libcpp_ctz(unsigned long __x) _NOEXCEPT { return __builtin_ctzl(__x); } 32 33inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 34int __libcpp_ctz(unsigned long long __x) _NOEXCEPT { return __builtin_ctzll(__x); } 35 36 37inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 38int __libcpp_clz(unsigned __x) _NOEXCEPT { return __builtin_clz(__x); } 39 40inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 41int __libcpp_clz(unsigned long __x) _NOEXCEPT { return __builtin_clzl(__x); } 42 43inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 44int __libcpp_clz(unsigned long long __x) _NOEXCEPT { return __builtin_clzll(__x); } 45 46# ifndef _LIBCPP_HAS_NO_INT128 47inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 48int __libcpp_clz(__uint128_t __x) _NOEXCEPT { 49 // The function is written in this form due to C++ constexpr limitations. 50 // The algorithm: 51 // - Test whether any bit in the high 64-bits is set 52 // - No bits set: 53 // - The high 64-bits contain 64 leading zeros, 54 // - Add the result of the low 64-bits. 55 // - Any bits set: 56 // - The number of leading zeros of the input is the number of leading 57 // zeros in the high 64-bits. 58 return ((__x >> 64) == 0) 59 ? (64 + __builtin_clzll(static_cast<unsigned long long>(__x))) 60 : __builtin_clzll(static_cast<unsigned long long>(__x >> 64)); 61} 62# endif 63 64inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 65int __libcpp_popcount(unsigned __x) _NOEXCEPT { return __builtin_popcount(__x); } 66 67inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 68int __libcpp_popcount(unsigned long __x) _NOEXCEPT { return __builtin_popcountl(__x); } 69 70inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 71int __libcpp_popcount(unsigned long long __x) _NOEXCEPT { return __builtin_popcountll(__x); } 72 73#else // _LIBCPP_COMPILER_MSVC 74 75// Precondition: __x != 0 76inline _LIBCPP_INLINE_VISIBILITY 77int __libcpp_ctz(unsigned __x) { 78 static_assert(sizeof(unsigned) == sizeof(unsigned long), ""); 79 static_assert(sizeof(unsigned long) == 4, ""); 80 unsigned long __where; 81 if (_BitScanForward(&__where, __x)) 82 return static_cast<int>(__where); 83 return 32; 84} 85 86inline _LIBCPP_INLINE_VISIBILITY 87int __libcpp_ctz(unsigned long __x) { 88 static_assert(sizeof(unsigned long) == sizeof(unsigned), ""); 89 return __ctz(static_cast<unsigned>(__x)); 90} 91 92inline _LIBCPP_INLINE_VISIBILITY 93int __libcpp_ctz(unsigned long long __x) { 94 unsigned long __where; 95#if defined(_LIBCPP_HAS_BITSCAN64) 96 if (_BitScanForward64(&__where, __x)) 97 return static_cast<int>(__where); 98#else 99 // Win32 doesn't have _BitScanForward64 so emulate it with two 32 bit calls. 100 if (_BitScanForward(&__where, static_cast<unsigned long>(__x))) 101 return static_cast<int>(__where); 102 if (_BitScanForward(&__where, static_cast<unsigned long>(__x >> 32))) 103 return static_cast<int>(__where + 32); 104#endif 105 return 64; 106} 107 108// Precondition: __x != 0 109inline _LIBCPP_INLINE_VISIBILITY 110int __libcpp_clz(unsigned __x) { 111 static_assert(sizeof(unsigned) == sizeof(unsigned long), ""); 112 static_assert(sizeof(unsigned long) == 4, ""); 113 unsigned long __where; 114 if (_BitScanReverse(&__where, __x)) 115 return static_cast<int>(31 - __where); 116 return 32; // Undefined Behavior. 117} 118 119inline _LIBCPP_INLINE_VISIBILITY 120int __libcpp_clz(unsigned long __x) { 121 static_assert(sizeof(unsigned) == sizeof(unsigned long), ""); 122 return __libcpp_clz(static_cast<unsigned>(__x)); 123} 124 125inline _LIBCPP_INLINE_VISIBILITY 126int __libcpp_clz(unsigned long long __x) { 127 unsigned long __where; 128#if defined(_LIBCPP_HAS_BITSCAN64) 129 if (_BitScanReverse64(&__where, __x)) 130 return static_cast<int>(63 - __where); 131#else 132 // Win32 doesn't have _BitScanReverse64 so emulate it with two 32 bit calls. 133 if (_BitScanReverse(&__where, static_cast<unsigned long>(__x >> 32))) 134 return static_cast<int>(63 - (__where + 32)); 135 if (_BitScanReverse(&__where, static_cast<unsigned long>(__x))) 136 return static_cast<int>(63 - __where); 137#endif 138 return 64; // Undefined Behavior. 139} 140 141inline _LIBCPP_INLINE_VISIBILITY int __libcpp_popcount(unsigned __x) { 142 static_assert(sizeof(unsigned) == 4, ""); 143 return __popcnt(__x); 144} 145 146inline _LIBCPP_INLINE_VISIBILITY int __libcpp_popcount(unsigned long __x) { 147 static_assert(sizeof(unsigned long) == 4, ""); 148 return __popcnt(__x); 149} 150 151inline _LIBCPP_INLINE_VISIBILITY int __libcpp_popcount(unsigned long long __x) { 152 static_assert(sizeof(unsigned long long) == 8, ""); 153 return __popcnt64(__x); 154} 155 156#endif // _LIBCPP_COMPILER_MSVC 157 158_LIBCPP_END_NAMESPACE_STD 159 160_LIBCPP_POP_MACROS 161 162#endif // _LIBCPP___BITS 163