xref: /aosp_15_r20/external/libcxx/include/bit (revision 58b9f456b02922dfdb1fad8a988d5fd8765ecb80)

// -*- C++ -*-
//===------------------------------ bit ----------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===---------------------------------------------------------------------===//

#ifndef _LIBCPP_BIT
#define _LIBCPP_BIT

/*
    bit synopsis

namespace std {

} // namespace std

*/

#include <__config>
#include <version>

#if defined(__IBMCPP__)
#include "support/ibm/support.h"
#endif
#if defined(_LIBCPP_COMPILER_MSVC)
#include <intrin.h>
#endif

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

#ifndef _LIBCPP_COMPILER_MSVC

inline _LIBCPP_INLINE_VISIBILITY
int __ctz(unsigned __x)           { return __builtin_ctz(__x); }

inline _LIBCPP_INLINE_VISIBILITY
int __ctz(unsigned long __x)      { return __builtin_ctzl(__x); }

inline _LIBCPP_INLINE_VISIBILITY
int __ctz(unsigned long long __x) { return __builtin_ctzll(__x); }


inline _LIBCPP_INLINE_VISIBILITY
int __clz(unsigned __x)           { return __builtin_clz(__x); }

inline _LIBCPP_INLINE_VISIBILITY
int __clz(unsigned long __x)      { return __builtin_clzl(__x); }

inline _LIBCPP_INLINE_VISIBILITY
int __clz(unsigned long long __x) { return __builtin_clzll(__x); }


inline _LIBCPP_INLINE_VISIBILITY
int __popcount(unsigned __x)           { return __builtin_popcount(__x); }

inline _LIBCPP_INLINE_VISIBILITY
int __popcount(unsigned long __x)      { return __builtin_popcountl(__x); }

inline _LIBCPP_INLINE_VISIBILITY
int __popcount(unsigned long long __x) { return __builtin_popcountll(__x); }

#else  // _LIBCPP_COMPILER_MSVC

// Precondition:  __x != 0
inline _LIBCPP_INLINE_VISIBILITY
int __ctz(unsigned __x) {
  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
  static_assert(sizeof(unsigned long) == 4, "");
  unsigned long __where;
  if (_BitScanForward(&__where, __x))
    return static_cast<int>(__where);
  return 32;
}

inline _LIBCPP_INLINE_VISIBILITY
int __ctz(unsigned long __x) {
    static_assert(sizeof(unsigned long) == sizeof(unsigned), "");
    return __ctz(static_cast<unsigned>(__x));
}

inline _LIBCPP_INLINE_VISIBILITY
int __ctz(unsigned long long __x) {
    unsigned long __where;
#if defined(_LIBCPP_HAS_BITSCAN64)
    (defined(_M_AMD64) || defined(__x86_64__))
  if (_BitScanForward64(&__where, __x))
    return static_cast<int>(__where);
#else
  // Win32 doesn't have _BitScanForward64 so emulate it with two 32 bit calls.
  if (_BitScanForward(&__where, static_cast<unsigned long>(__x)))
    return static_cast<int>(__where);
  if (_BitScanForward(&__where, static_cast<unsigned long>(__x >> 32)))
    return static_cast<int>(__where + 32);
#endif
  return 64;
}

// Precondition:  __x != 0
inline _LIBCPP_INLINE_VISIBILITY
int __clz(unsigned __x) {
  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
  static_assert(sizeof(unsigned long) == 4, "");
  unsigned long __where;
  if (_BitScanReverse(&__where, __x))
    return static_cast<int>(31 - __where);
  return 32; // Undefined Behavior.
}

inline _LIBCPP_INLINE_VISIBILITY
int __clz(unsigned long __x) {
    static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
    return __clz(static_cast<unsigned>(__x));
}

inline _LIBCPP_INLINE_VISIBILITY
int __clz(unsigned long long __x) {
  unsigned long __where;
#if defined(_LIBCPP_HAS_BITSCAN64)
  if (_BitScanReverse64(&__where, __x))
    return static_cast<int>(63 - __where);
#else
  // Win32 doesn't have _BitScanReverse64 so emulate it with two 32 bit calls.
  if (_BitScanReverse(&__where, static_cast<unsigned long>(__x >> 32)))
    return static_cast<int>(63 - (__where + 32));
  if (_BitScanReverse(&__where, static_cast<unsigned long>(__x)))
    return static_cast<int>(63 - __where);
#endif
  return 64; // Undefined Behavior.
}

inline _LIBCPP_INLINE_VISIBILITY int __popcount(unsigned __x) {
  static_assert(sizeof(unsigned) == 4, "");
  return __popcnt(__x);
}

inline _LIBCPP_INLINE_VISIBILITY int __popcount(unsigned long __x) {
  static_assert(sizeof(unsigned long) == 4, "");
  return __popcnt(__x);
}

inline _LIBCPP_INLINE_VISIBILITY int __popcount(unsigned long long __x) {
  static_assert(sizeof(unsigned long long) == 8, "");
  return __popcnt64(__x);
}

#endif // _LIBCPP_COMPILER_MSVC

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP_BIT