Add libc++ and libc++abi to third-party.

third_party/libcxx/include/__bit_reference

Index: third_party/libcxx/include/__bit_reference
===================================================================
--- third_party/libcxx/include/__bit_reference	(revision 0)
+++ third_party/libcxx/include/__bit_reference	(revision 0)
@@ -0,0 +1,1287 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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_REFERENCE
+#define _LIBCPP___BIT_REFERENCE
+
+#include <__config>
+#include <algorithm>
+
+#include <__undef_min_max>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Cp, bool _IsConst, typename _Cp::__storage_type = 0> class __bit_iterator;
+template <class _Cp> class __bit_const_reference;
+
+template <class _Tp>
+struct __has_storage_type
+{
+    static const bool value = false;
+};
+
+template <class _Cp, bool = __has_storage_type<_Cp>::value>
+class __bit_reference
+{
+    typedef typename _Cp::__storage_type    __storage_type;
+    typedef typename _Cp::__storage_pointer __storage_pointer;
+
+    __storage_pointer __seg_;
+    __storage_type    __mask_;
+
+#if defined(__clang__) || defined(__IBMCPP__) || defined(_LIBCPP_MSVC)
+    friend typename _Cp::__self;
+#else
+    friend class _Cp::__self;
+#endif
+    friend class __bit_const_reference<_Cp>;
+    friend class __bit_iterator<_Cp, false>;
+public:
+    _LIBCPP_INLINE_VISIBILITY operator bool() const _NOEXCEPT
+        {return static_cast<bool>(*__seg_ & __mask_);}
+    _LIBCPP_INLINE_VISIBILITY bool operator ~() const _NOEXCEPT
+        {return !static_cast<bool>(*this);}
+
+    _LIBCPP_INLINE_VISIBILITY
+    __bit_reference& operator=(bool __x) _NOEXCEPT
+    {
+        if (__x)
+            *__seg_ |= __mask_;
+        else
+            *__seg_ &= ~__mask_;
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __bit_reference& operator=(const __bit_reference& __x) _NOEXCEPT
+        {return operator=(static_cast<bool>(__x));}
+
+    _LIBCPP_INLINE_VISIBILITY void flip() _NOEXCEPT {*__seg_ ^= __mask_;}
+    _LIBCPP_INLINE_VISIBILITY __bit_iterator<_Cp, false> operator&() const _NOEXCEPT
+        {return __bit_iterator<_Cp, false>(__seg_, static_cast<unsigned>(__ctz(__mask_)));}
+private:
+    _LIBCPP_INLINE_VISIBILITY
+    __bit_reference(__storage_pointer __s, __storage_type __m) _NOEXCEPT
+        : __seg_(__s), __mask_(__m) {}
+};
+
+template <class _Cp>
+class __bit_reference<_Cp, false>
+{
+};
+
+template <class _Cp>
+inline _LIBCPP_INLINE_VISIBILITY
+void
+swap(__bit_reference<_Cp> __x, __bit_reference<_Cp> __y) _NOEXCEPT
+{
+    bool __t = __x;
+    __x = __y;
+    __y = __t;
+}
+
+template <class _Cp, class _Dp>
+inline _LIBCPP_INLINE_VISIBILITY
+void
+swap(__bit_reference<_Cp> __x, __bit_reference<_Dp> __y) _NOEXCEPT
+{
+    bool __t = __x;
+    __x = __y;
+    __y = __t;
+}
+
+template <class _Cp>
+inline _LIBCPP_INLINE_VISIBILITY
+void
+swap(__bit_reference<_Cp> __x, bool& __y) _NOEXCEPT
+{
+    bool __t = __x;
+    __x = __y;
+    __y = __t;
+}
+
+template <class _Cp>
+inline _LIBCPP_INLINE_VISIBILITY
+void
+swap(bool& __x, __bit_reference<_Cp> __y) _NOEXCEPT
+{
+    bool __t = __x;
+    __x = __y;
+    __y = __t;
+}
+
+template <class _Cp>
+class __bit_const_reference
+{
+    typedef typename _Cp::__storage_type          __storage_type;
+    typedef typename _Cp::__const_storage_pointer __storage_pointer;
+
+    __storage_pointer        __seg_;
+    __storage_type __mask_;
+
+#if defined(__clang__) || defined(__IBMCPP__) || defined(_LIBCPP_MSVC)
+    friend typename _Cp::__self;
+#else
+    friend class _Cp::__self;
+#endif
+    friend class __bit_iterator<_Cp, true>;
+public:
+    _LIBCPP_INLINE_VISIBILITY
+    __bit_const_reference(const __bit_reference<_Cp>& __x) _NOEXCEPT
+        : __seg_(__x.__seg_), __mask_(__x.__mask_) {}
+
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR operator bool() const _NOEXCEPT
+        {return static_cast<bool>(*__seg_ & __mask_);}
+
+    _LIBCPP_INLINE_VISIBILITY __bit_iterator<_Cp, true> operator&() const _NOEXCEPT
+        {return __bit_iterator<_Cp, true>(__seg_, static_cast<unsigned>(__ctz(__mask_)));}
+private:
+    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_CONSTEXPR
+    __bit_const_reference(__storage_pointer __s, __storage_type __m) _NOEXCEPT
+        : __seg_(__s), __mask_(__m) {}
+
+    __bit_const_reference& operator=(const __bit_const_reference& __x);
+};
+
+// find
+
+template <class _Cp, bool _IsConst>
+__bit_iterator<_Cp, _IsConst>
+__find_bool_true(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n)
+{
+    typedef __bit_iterator<_Cp, _IsConst> _It;
+    typedef typename _It::__storage_type __storage_type;
+    static const unsigned __bits_per_word = _It::__bits_per_word;
+    // do first partial word
+    if (__first.__ctz_ != 0)
+    {
+        __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
+        __storage_type __dn = _VSTD::min(__clz_f, __n);
+        __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
+        __storage_type __b = *__first.__seg_ & __m;
+        if (__b)
+            return _It(__first.__seg_, static_cast<unsigned>(_VSTD::__ctz(__b)));
+        if (__n == __dn)
+            return _It(__first.__seg_, __first.__ctz_ + __n);
+        __n -= __dn;
+        ++__first.__seg_;
+    }
+    // do middle whole words
+    for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word)
+        if (*__first.__seg_)
+            return _It(__first.__seg_, static_cast<unsigned>(_VSTD::__ctz(*__first.__seg_)));
+    // do last partial word
+    if (__n > 0)
+    {
+        __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
+        __storage_type __b = *__first.__seg_ & __m;
+        if (__b)
+            return _It(__first.__seg_, static_cast<unsigned>(_VSTD::__ctz(__b)));
+    }
+    return _It(__first.__seg_, static_cast<unsigned>(__n));
+}
+
+template <class _Cp, bool _IsConst>
+__bit_iterator<_Cp, _IsConst>
+__find_bool_false(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n)
+{
+    typedef __bit_iterator<_Cp, _IsConst> _It;
+    typedef typename _It::__storage_type __storage_type;
+    static const unsigned __bits_per_word = _It::__bits_per_word;
+    // do first partial word
+    if (__first.__ctz_ != 0)
+    {
+        __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
+        __storage_type __dn = _VSTD::min(__clz_f, __n);
+        __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
+        __storage_type __b = ~*__first.__seg_ & __m;
+        if (__b)
+            return _It(__first.__seg_, static_cast<unsigned>(_VSTD::__ctz(__b)));
+        if (__n == __dn)
+            return _It(__first.__seg_, __first.__ctz_ + __n);
+        __n -= __dn;
+        ++__first.__seg_;
+    }
+    // do middle whole words
+    for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word)
+    {
+        __storage_type __b = ~*__first.__seg_;
+        if (__b)
+            return _It(__first.__seg_, static_cast<unsigned>(_VSTD::__ctz(__b)));
+    }
+    // do last partial word
+    if (__n > 0)
+    {
+        __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
+        __storage_type __b = ~*__first.__seg_ & __m;
+        if (__b)
+            return _It(__first.__seg_, static_cast<unsigned>(_VSTD::__ctz(__b)));
+    }
+    return _It(__first.__seg_, static_cast<unsigned>(__n));
+}
+
+template <class _Cp, bool _IsConst, class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+__bit_iterator<_Cp, _IsConst>
+find(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, const _Tp& __value_)
+{
+    if (static_cast<bool>(__value_))
+        return __find_bool_true(__first, static_cast<typename _Cp::size_type>(__last - __first));
+    return __find_bool_false(__first, static_cast<typename _Cp::size_type>(__last - __first));
+}
+
+// count
+
+template <class _Cp, bool _IsConst>
+typename __bit_iterator<_Cp, _IsConst>::difference_type
+__count_bool_true(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n)
+{
+    typedef __bit_iterator<_Cp, _IsConst> _It;
+    typedef typename _It::__storage_type __storage_type;
+    typedef typename _It::difference_type difference_type;
+    static const unsigned __bits_per_word = _It::__bits_per_word;
+    difference_type __r = 0;
+    // do first partial word
+    if (__first.__ctz_ != 0)
+    {
+        __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
+        __storage_type __dn = _VSTD::min(__clz_f, __n);
+        __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
+        __r = _VSTD::__pop_count(*__first.__seg_ & __m);
+        __n -= __dn;
+        ++__first.__seg_;
+    }
+    // do middle whole words
+    for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word)
+        __r += _VSTD::__pop_count(*__first.__seg_);
+    // do last partial word
+    if (__n > 0)
+    {
+        __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
+        __r += _VSTD::__pop_count(*__first.__seg_ & __m);
+    }
+    return __r;
+}
+
+template <class _Cp, bool _IsConst>
+typename __bit_iterator<_Cp, _IsConst>::difference_type
+__count_bool_false(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n)
+{
+    typedef __bit_iterator<_Cp, _IsConst> _It;
+    typedef typename _It::__storage_type __storage_type;
+    typedef typename _It::difference_type difference_type;
+    static const unsigned __bits_per_word = _It::__bits_per_word;
+    difference_type __r = 0;
+    // do first partial word
+    if (__first.__ctz_ != 0)
+    {
+        __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
+        __storage_type __dn = _VSTD::min(__clz_f, __n);
+        __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
+        __r = _VSTD::__pop_count(~*__first.__seg_ & __m);
+        __n -= __dn;
+        ++__first.__seg_;
+    }
+    // do middle whole words
+    for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word)
+        __r += _VSTD::__pop_count(~*__first.__seg_);
+    // do last partial word
+    if (__n > 0)
+    {
+        __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
+        __r += _VSTD::__pop_count(~*__first.__seg_ & __m);
+    }
+    return __r;
+}
+
+template <class _Cp, bool _IsConst, class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __bit_iterator<_Cp, _IsConst>::difference_type
+count(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, const _Tp& __value_)
+{
+    if (static_cast<bool>(__value_))
+        return __count_bool_true(__first, static_cast<typename _Cp::size_type>(__last - __first));
+    return __count_bool_false(__first, static_cast<typename _Cp::size_type>(__last - __first));
+}
+
+// fill_n
+
+template <class _Cp>
+void
+__fill_n_false(__bit_iterator<_Cp, false> __first, typename _Cp::size_type __n)
+{
+    typedef __bit_iterator<_Cp, false> _It;
+    typedef typename _It::__storage_type __storage_type;
+    static const unsigned __bits_per_word = _It::__bits_per_word;
+    // do first partial word
+    if (__first.__ctz_ != 0)
+    {
+        __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
+        __storage_type __dn = _VSTD::min(__clz_f, __n);
+        __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
+        *__first.__seg_ &= ~__m;
+        __n -= __dn;
+        ++__first.__seg_;
+    }
+    // do middle whole words
+    __storage_type __nw = __n / __bits_per_word;
+    _VSTD::memset(_VSTD::__to_raw_pointer(__first.__seg_), 0, __nw * sizeof(__storage_type));
+    __n -= __nw * __bits_per_word;
+    // do last partial word
+    if (__n > 0)
+    {
+        __first.__seg_ += __nw;
+        __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
+        *__first.__seg_ &= ~__m;
+    }
+}
+
+template <class _Cp>
+void
+__fill_n_true(__bit_iterator<_Cp, false> __first, typename _Cp::size_type __n)
+{
+    typedef __bit_iterator<_Cp, false> _It;
+    typedef typename _It::__storage_type __storage_type;
+    static const unsigned __bits_per_word = _It::__bits_per_word;
+    // do first partial word
+    if (__first.__ctz_ != 0)
+    {
+        __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
+        __storage_type __dn = _VSTD::min(__clz_f, __n);
+        __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
+        *__first.__seg_ |= __m;
+        __n -= __dn;
+        ++__first.__seg_;
+    }
+    // do middle whole words
+    __storage_type __nw = __n / __bits_per_word;
+    _VSTD::memset(_VSTD::__to_raw_pointer(__first.__seg_), -1, __nw * sizeof(__storage_type));
+    __n -= __nw * __bits_per_word;
+    // do last partial word
+    if (__n > 0)
+    {
+        __first.__seg_ += __nw;
+        __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
+        *__first.__seg_ |= __m;
+    }
+}
+
+template <class _Cp>
+inline _LIBCPP_INLINE_VISIBILITY
+void
+fill_n(__bit_iterator<_Cp, false> __first, typename _Cp::size_type __n, bool __value_)
+{
+    if (__n > 0)
+    {
+        if (__value_)
+            __fill_n_true(__first, __n);
+        else
+            __fill_n_false(__first, __n);
+    }
+}
+
+// fill
+
+template <class _Cp>
+inline _LIBCPP_INLINE_VISIBILITY
+void
+fill(__bit_iterator<_Cp, false> __first, __bit_iterator<_Cp, false> __last, bool __value_)
+{
+    _VSTD::fill_n(__first, static_cast<typename _Cp::size_type>(__last - __first), __value_);
+}
+
+// copy
+
+template <class _Cp, bool _IsConst>
+__bit_iterator<_Cp, false>
+__copy_aligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last,
+                                                     __bit_iterator<_Cp, false> __result)
+{
+    typedef __bit_iterator<_Cp, _IsConst> _In;
+    typedef  typename _In::difference_type difference_type;
+    typedef typename _In::__storage_type __storage_type;
+    static const unsigned __bits_per_word = _In::__bits_per_word;
+    difference_type __n = __last - __first;
+    if (__n > 0)
+    {
+        // do first word
+        if (__first.__ctz_ != 0)
+        {
+            unsigned __clz = __bits_per_word - __first.__ctz_;
+            difference_type __dn = _VSTD::min(static_cast<difference_type>(__clz), __n);
+            __n -= __dn;
+            __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz - __dn));
+            __storage_type __b = *__first.__seg_ & __m;
+            *__result.__seg_ &= ~__m;
+            *__result.__seg_ |= __b;
+            __result.__seg_ += (__dn + __result.__ctz_) / __bits_per_word;
+            __result.__ctz_ = static_cast<unsigned>((__dn + __result.__ctz_)  % __bits_per_word);
+            ++__first.__seg_;
+            // __first.__ctz_ = 0;
+        }
+        // __first.__ctz_ == 0;
+        // do middle words
+        __storage_type __nw = __n / __bits_per_word;
+        _VSTD::memmove(_VSTD::__to_raw_pointer(__result.__seg_),
+                       _VSTD::__to_raw_pointer(__first.__seg_),
+                       __nw * sizeof(__storage_type));
+        __n -= __nw * __bits_per_word;
+        __result.__seg_ += __nw;
+        // do last word
+        if (__n > 0)
+        {
+            __first.__seg_ += __nw;
+            __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
+            __storage_type __b = *__first.__seg_ & __m;
+            *__result.__seg_ &= ~__m;
+            *__result.__seg_ |= __b;
+            __result.__ctz_ = static_cast<unsigned>(__n);
+        }
+    }
+    return __result;
+}
+
+template <class _Cp, bool _IsConst>
+__bit_iterator<_Cp, false>
+__copy_unaligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last,
+                                                       __bit_iterator<_Cp, false> __result)
+{
+    typedef __bit_iterator<_Cp, _IsConst> _In;
+    typedef  typename _In::difference_type difference_type;
+    typedef typename _In::__storage_type __storage_type;
+    static const unsigned __bits_per_word = _In::__bits_per_word;
+    difference_type __n = __last - __first;
+    if (__n > 0)
+    {
+        // do first word
+        if (__first.__ctz_ != 0)
+        {
+            unsigned __clz_f = __bits_per_word - __first.__ctz_;
+            difference_type __dn = _VSTD::min(static_cast<difference_type>(__clz_f), __n);
+            __n -= __dn;
+            __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
+            __storage_type __b = *__first.__seg_ & __m;
+            unsigned __clz_r = __bits_per_word - __result.__ctz_;
+            __storage_type __ddn = _VSTD::min<__storage_type>(__dn, __clz_r);
+            __m = (~__storage_type(0) << __result.__ctz_) & (~__storage_type(0) >> (__clz_r - __ddn));
+            *__result.__seg_ &= ~__m;
+            if (__result.__ctz_ > __first.__ctz_)
+                *__result.__seg_ |= __b << (__result.__ctz_ - __first.__ctz_);
+            else
+                *__result.__seg_ |= __b >> (__first.__ctz_ - __result.__ctz_);
+            __result.__seg_ += (__ddn + __result.__ctz_) / __bits_per_word;
+            __result.__ctz_ = static_cast<unsigned>((__ddn + __result.__ctz_)  % __bits_per_word);
+            __dn -= __ddn;
+            if (__dn > 0)
+            {
+                __m = ~__storage_type(0) >> (__bits_per_word - __dn);
+                *__result.__seg_ &= ~__m;
+                *__result.__seg_ |= __b >> (__first.__ctz_ + __ddn);
+                __result.__ctz_ = static_cast<unsigned>(__dn);
+            }
+            ++__first.__seg_;
+            // __first.__ctz_ = 0;
+        }
+        // __first.__ctz_ == 0;
+        // do middle words
+        unsigned __clz_r = __bits_per_word - __result.__ctz_;
+        __storage_type __m = ~__storage_type(0) << __result.__ctz_;
+        for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first.__seg_)
+        {
+            __storage_type __b = *__first.__seg_;
+            *__result.__seg_ &= ~__m;
+            *__result.__seg_ |= __b << __result.__ctz_;
+            ++__result.__seg_;
+            *__result.__seg_ &= __m;
+            *__result.__seg_ |= __b >> __clz_r;
+        }
+        // do last word
+        if (__n > 0)
+        {
+            __m = ~__storage_type(0) >> (__bits_per_word - __n);
+            __storage_type __b = *__first.__seg_ & __m;
+            __storage_type __dn = _VSTD::min(__n, static_cast<difference_type>(__clz_r));
+            __m = (~__storage_type(0) << __result.__ctz_) & (~__storage_type(0) >> (__clz_r - __dn));
+            *__result.__seg_ &= ~__m;
+            *__result.__seg_ |= __b << __result.__ctz_;
+            __result.__seg_ += (__dn + __result.__ctz_) / __bits_per_word;
+            __result.__ctz_ = static_cast<unsigned>((__dn + __result.__ctz_)  % __bits_per_word);
+            __n -= __dn;
+            if (__n > 0)
+            {
+                __m = ~__storage_type(0) >> (__bits_per_word - __n);
+                *__result.__seg_ &= ~__m;
+                *__result.__seg_ |= __b >> __dn;
+                __result.__ctz_ = static_cast<unsigned>(__n);
+            }
+        }
+    }
+    return __result;
+}
+
+template <class _Cp, bool _IsConst>
+inline _LIBCPP_INLINE_VISIBILITY
+__bit_iterator<_Cp, false>
+copy(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result)
+{
+    if (__first.__ctz_ == __result.__ctz_)
+        return __copy_aligned(__first, __last, __result);
+    return __copy_unaligned(__first, __last, __result);
+}
+
+// copy_backward
+
+template <class _Cp, bool _IsConst>
+__bit_iterator<_Cp, false>
+__copy_backward_aligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last,
+                                                     __bit_iterator<_Cp, false> __result)
+{
+    typedef __bit_iterator<_Cp, _IsConst> _In;
+    typedef  typename _In::difference_type difference_type;
+    typedef typename _In::__storage_type __storage_type;
+    static const unsigned __bits_per_word = _In::__bits_per_word;
+    difference_type __n = __last - __first;
+    if (__n > 0)
+    {
+        // do first word
+        if (__last.__ctz_ != 0)
+        {
+            difference_type __dn = _VSTD::min(static_cast<difference_type>(__last.__ctz_), __n);
+            __n -= __dn;
+            unsigned __clz = __bits_per_word - __last.__ctz_;
+            __storage_type __m = (~__storage_type(0) << (__last.__ctz_ - __dn)) & (~__storage_type(0) >> __clz);
+            __storage_type __b = *__last.__seg_ & __m;
+            *__result.__seg_ &= ~__m;
+            *__result.__seg_ |= __b;
+            __result.__ctz_ = static_cast<unsigned>(((-__dn & (__bits_per_word - 1)) +
+                                                       __result.__ctz_)  % __bits_per_word);
+            // __last.__ctz_ = 0
+         }
+        // __last.__ctz_ == 0 || __n == 0
+        // __result.__ctz_ == 0 || __n == 0
+        // do middle words
+        __storage_type __nw = __n / __bits_per_word;
+        __result.__seg_ -= __nw;
+        __last.__seg_ -= __nw;
+        _VSTD::memmove(_VSTD::__to_raw_pointer(__result.__seg_),
+                       _VSTD::__to_raw_pointer(__last.__seg_),
+                       __nw * sizeof(__storage_type));
+        __n -= __nw * __bits_per_word;
+        // do last word
+        if (__n > 0)
+        {
+            __storage_type __m = ~__storage_type(0) << (__bits_per_word - __n);
+            __storage_type __b = *--__last.__seg_ & __m;
+            *--__result.__seg_ &= ~__m;
+            *__result.__seg_ |= __b;
+            __result.__ctz_ = static_cast<unsigned>(-__n & (__bits_per_word - 1));
+        }
+    }
+    return __result;
+}
+
+template <class _Cp, bool _IsConst>
+__bit_iterator<_Cp, false>
+__copy_backward_unaligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last,
+                                                       __bit_iterator<_Cp, false> __result)
+{
+    typedef __bit_iterator<_Cp, _IsConst> _In;
+    typedef  typename _In::difference_type difference_type;
+    typedef typename _In::__storage_type __storage_type;
+    static const unsigned __bits_per_word = _In::__bits_per_word;
+    difference_type __n = __last - __first;
+    if (__n > 0)
+    {
+        // do first word
+        if (__last.__ctz_ != 0)
+        {
+            difference_type __dn = _VSTD::min(static_cast<difference_type>(__last.__ctz_), __n);
+            __n -= __dn;
+            unsigned __clz_l = __bits_per_word - __last.__ctz_;
+            __storage_type __m = (~__storage_type(0) << (__last.__ctz_ - __dn)) & (~__storage_type(0) >> __clz_l);
+            __storage_type __b = *__last.__seg_ & __m;
+            unsigned __clz_r = __bits_per_word - __result.__ctz_;
+            __storage_type __ddn = _VSTD::min(__dn, static_cast<difference_type>(__result.__ctz_));
+            if (__ddn > 0)
+            {
+                __m = (~__storage_type(0) << (__result.__ctz_ - __ddn)) & (~__storage_type(0) >> __clz_r);
+                *__result.__seg_ &= ~__m;
+                if (__result.__ctz_ > __last.__ctz_)
+                    *__result.__seg_ |= __b << (__result.__ctz_ - __last.__ctz_);
+                else
+                    *__result.__seg_ |= __b >> (__last.__ctz_ - __result.__ctz_);
+                __result.__ctz_ = static_cast<unsigned>(((-__ddn & (__bits_per_word - 1)) +
+                                                         __result.__ctz_)  % __bits_per_word);
+                __dn -= __ddn;
+            }
+            if (__dn > 0)
+            {
+                // __result.__ctz_ == 0
+                --__result.__seg_;
+                __result.__ctz_ = static_cast<unsigned>(-__dn & (__bits_per_word - 1));
+                __m = ~__storage_type(0) << __result.__ctz_;
+                *__result.__seg_ &= ~__m;
+                __last.__ctz_ -= __dn + __ddn;
+                *__result.__seg_ |= __b << (__result.__ctz_ - __last.__ctz_);
+            }
+            // __last.__ctz_ = 0
+         }
+        // __last.__ctz_ == 0 || __n == 0
+        // __result.__ctz_ != 0 || __n == 0
+        // do middle words
+        unsigned __clz_r = __bits_per_word - __result.__ctz_;
+        __storage_type __m = ~__storage_type(0) >> __clz_r;
+        for (; __n >= __bits_per_word; __n -= __bits_per_word)
+        {
+            __storage_type __b = *--__last.__seg_;
+            *__result.__seg_ &= ~__m;
+            *__result.__seg_ |= __b >> __clz_r;
+            *--__result.__seg_ &= __m;
+            *__result.__seg_ |= __b << __result.__ctz_;
+        }
+        // do last word
+        if (__n > 0)
+        {
+            __m = ~__storage_type(0) << (__bits_per_word - __n);
+            __storage_type __b = *--__last.__seg_ & __m;
+            __clz_r = __bits_per_word - __result.__ctz_;
+            __storage_type __dn = _VSTD::min(__n, static_cast<difference_type>(__result.__ctz_));
+            __m = (~__storage_type(0) << (__result.__ctz_ - __dn)) & (~__storage_type(0) >> __clz_r);
+            *__result.__seg_ &= ~__m;
+            *__result.__seg_ |= __b >> (__bits_per_word - __result.__ctz_);
+            __result.__ctz_ = static_cast<unsigned>(((-__dn & (__bits_per_word - 1)) +
+                                                     __result.__ctz_)  % __bits_per_word);
+            __n -= __dn;
+            if (__n > 0)
+            {
+                // __result.__ctz_ == 0
+                --__result.__seg_;
+                __result.__ctz_ = static_cast<unsigned>(-__n & (__bits_per_word - 1));
+                __m = ~__storage_type(0) << __result.__ctz_;
+                *__result.__seg_ &= ~__m;
+                *__result.__seg_ |= __b << (__result.__ctz_ - (__bits_per_word - __n - __dn));
+            }
+        }
+    }
+    return __result;
+}
+
+template <class _Cp, bool _IsConst>
+inline _LIBCPP_INLINE_VISIBILITY
+__bit_iterator<_Cp, false>
+copy_backward(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result)
+{
+    if (__last.__ctz_ == __result.__ctz_)
+        return __copy_backward_aligned(__first, __last, __result);
+    return __copy_backward_unaligned(__first, __last, __result);
+}
+
+// move
+
+template <class _Cp, bool _IsConst>
+inline _LIBCPP_INLINE_VISIBILITY
+__bit_iterator<_Cp, false>
+move(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result)
+{
+    return _VSTD::copy(__first, __last, __result);
+}
+
+// move_backward
+
+template <class _Cp, bool _IsConst>
+inline _LIBCPP_INLINE_VISIBILITY
+__bit_iterator<_Cp, false>
+move_backward(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result)
+{
+    return _VSTD::copy(__first, __last, __result);
+}
+
+// swap_ranges
+
+template <class __C1, class __C2>
+__bit_iterator<__C2, false>
+__swap_ranges_aligned(__bit_iterator<__C1, false> __first, __bit_iterator<__C1, false> __last,
+                      __bit_iterator<__C2, false> __result)
+{
+    typedef __bit_iterator<__C1, false> _I1;
+    typedef  typename _I1::difference_type difference_type;
+    typedef typename _I1::__storage_type __storage_type;
+    static const unsigned __bits_per_word = _I1::__bits_per_word;
+    difference_type __n = __last - __first;
+    if (__n > 0)
+    {
+        // do first word
+        if (__first.__ctz_ != 0)
+        {
+            unsigned __clz = __bits_per_word - __first.__ctz_;
+            difference_type __dn = _VSTD::min(static_cast<difference_type>(__clz), __n);
+            __n -= __dn;
+            __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz - __dn));
+            __storage_type __b1 = *__first.__seg_ & __m;
+            *__first.__seg_ &= ~__m;
+            __storage_type __b2 = *__result.__seg_ & __m;
+            *__result.__seg_ &= ~__m;
+            *__result.__seg_ |= __b1;
+            *__first.__seg_  |= __b2;
+            __result.__seg_ += (__dn + __result.__ctz_) / __bits_per_word;
+            __result.__ctz_ = static_cast<unsigned>((__dn + __result.__ctz_)  % __bits_per_word);
+            ++__first.__seg_;
+            // __first.__ctz_ = 0;
+        }
+        // __first.__ctz_ == 0;
+        // do middle words
+        for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first.__seg_, ++__result.__seg_)
+            swap(*__first.__seg_, *__result.__seg_);
+        // do last word
+        if (__n > 0)
+        {
+            __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
+            __storage_type __b1 = *__first.__seg_ & __m;
+            *__first.__seg_ &= ~__m;
+            __storage_type __b2 = *__result.__seg_ & __m;
+            *__result.__seg_ &= ~__m;
+            *__result.__seg_ |= __b1;
+            *__first.__seg_  |= __b2;
+            __result.__ctz_ = static_cast<unsigned>(__n);
+        }
+    }
+    return __result;
+}
+
+template <class __C1, class __C2>
+__bit_iterator<__C2, false>
+__swap_ranges_unaligned(__bit_iterator<__C1, false> __first, __bit_iterator<__C1, false> __last,
+                        __bit_iterator<__C2, false> __result)
+{
+    typedef __bit_iterator<__C1, false> _I1;
+    typedef  typename _I1::difference_type difference_type;
+    typedef typename _I1::__storage_type __storage_type;
+    static const unsigned __bits_per_word = _I1::__bits_per_word;
+    difference_type __n = __last - __first;
+    if (__n > 0)
+    {
+        // do first word
+        if (__first.__ctz_ != 0)
+        {
+            unsigned __clz_f = __bits_per_word - __first.__ctz_;
+            difference_type __dn = _VSTD::min(static_cast<difference_type>(__clz_f), __n);
+            __n -= __dn;
+            __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
+            __storage_type __b1 = *__first.__seg_ & __m;
+            *__first.__seg_ &= ~__m;
+            unsigned __clz_r = __bits_per_word - __result.__ctz_;
+            __storage_type __ddn = _VSTD::min<__storage_type>(__dn, __clz_r);
+            __m = (~__storage_type(0) << __result.__ctz_) & (~__storage_type(0) >> (__clz_r - __ddn));
+            __storage_type __b2 = *__result.__seg_ & __m;
+            *__result.__seg_ &= ~__m;
+            if (__result.__ctz_ > __first.__ctz_)
+            {
+                unsigned __s = __result.__ctz_ - __first.__ctz_;
+                *__result.__seg_ |= __b1 << __s;
+                *__first.__seg_  |= __b2 >> __s;
+            }
+            else
+            {
+                unsigned __s = __first.__ctz_ - __result.__ctz_;
+                *__result.__seg_ |= __b1 >> __s;
+                *__first.__seg_  |= __b2 << __s;
+            }
+            __result.__seg_ += (__ddn + __result.__ctz_) / __bits_per_word;
+            __result.__ctz_ = static_cast<unsigned>((__ddn + __result.__ctz_)  % __bits_per_word);
+            __dn -= __ddn;
+            if (__dn > 0)
+            {
+                __m = ~__storage_type(0) >> (__bits_per_word - __dn);
+                __b2 = *__result.__seg_ & __m;
+                *__result.__seg_ &= ~__m;
+                unsigned __s = __first.__ctz_ + __ddn;
+                *__result.__seg_ |= __b1 >> __s;
+                *__first.__seg_  |= __b2 << __s;
+                __result.__ctz_ = static_cast<unsigned>(__dn);
+            }
+            ++__first.__seg_;
+            // __first.__ctz_ = 0;
+        }
+        // __first.__ctz_ == 0;
+        // do middle words
+        __storage_type __m = ~__storage_type(0) << __result.__ctz_;
+        unsigned __clz_r = __bits_per_word - __result.__ctz_;
+        for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first.__seg_)
+        {
+            __storage_type __b1 = *__first.__seg_;
+            __storage_type __b2 = *__result.__seg_ & __m;
+            *__result.__seg_ &= ~__m;
+            *__result.__seg_ |= __b1 << __result.__ctz_;
+            *__first.__seg_  = __b2 >> __result.__ctz_;
+            ++__result.__seg_;
+            __b2 = *__result.__seg_ & ~__m;
+            *__result.__seg_ &= __m;
+            *__result.__seg_ |= __b1 >> __clz_r;
+            *__first.__seg_  |= __b2 << __clz_r;
+        }
+        // do last word
+        if (__n > 0)
+        {
+            __m = ~__storage_type(0) >> (__bits_per_word - __n);
+            __storage_type __b1 = *__first.__seg_ & __m;
+            *__first.__seg_ &= ~__m;
+            __storage_type __dn = _VSTD::min<__storage_type>(__n, __clz_r);
+            __m = (~__storage_type(0) << __result.__ctz_) & (~__storage_type(0) >> (__clz_r - __dn));
+            __storage_type __b2 = *__result.__seg_ & __m;
+            *__result.__seg_ &= ~__m;
+            *__result.__seg_ |= __b1 << __result.__ctz_;
+            *__first.__seg_  |= __b2 >> __result.__ctz_;
+            __result.__seg_ += (__dn + __result.__ctz_) / __bits_per_word;
+            __result.__ctz_ = static_cast<unsigned>((__dn + __result.__ctz_)  % __bits_per_word);
+            __n -= __dn;
+            if (__n > 0)
+            {
+                __m = ~__storage_type(0) >> (__bits_per_word - __n);
+                __b2 = *__result.__seg_ & __m;
+                *__result.__seg_ &= ~__m;
+                *__result.__seg_ |= __b1 >> __dn;
+                *__first.__seg_  |= __b2 << __dn;
+                __result.__ctz_ = static_cast<unsigned>(__n);
+            }
+        }
+    }
+    return __result;
+}
+
+template <class __C1, class __C2>
+inline _LIBCPP_INLINE_VISIBILITY
+__bit_iterator<__C2, false>
+swap_ranges(__bit_iterator<__C1, false> __first1, __bit_iterator<__C1, false> __last1,
+            __bit_iterator<__C2, false> __first2)
+{
+    if (__first1.__ctz_ == __first2.__ctz_)
+        return __swap_ranges_aligned(__first1, __last1, __first2);
+    return __swap_ranges_unaligned(__first1, __last1, __first2);
+}
+
+// rotate
+
+template <class _Cp>
+struct __bit_array
+{
+    typedef typename _Cp::difference_type difference_type;
+    typedef typename _Cp::__storage_type  __storage_type;
+    typedef typename _Cp::__storage_pointer __storage_pointer;
+    typedef typename _Cp::iterator        iterator;
+    static const unsigned __bits_per_word = _Cp::__bits_per_word;
+    static const unsigned _Np = 4;
+
+    difference_type __size_;
+    __storage_type __word_[_Np];
+
+    _LIBCPP_INLINE_VISIBILITY static difference_type capacity()
+        {return static_cast<difference_type>(_Np * __bits_per_word);}
+    _LIBCPP_INLINE_VISIBILITY explicit __bit_array(difference_type __s) : __size_(__s) {}
+    _LIBCPP_INLINE_VISIBILITY iterator begin()
+    {
+        return iterator(pointer_traits<__storage_pointer>::pointer_to(__word_[0]), 0);
+    }
+    _LIBCPP_INLINE_VISIBILITY iterator end()
+    {
+        return iterator(pointer_traits<__storage_pointer>::pointer_to(__word_[0]) + __size_ / __bits_per_word,
+                                                  static_cast<unsigned>(__size_ % __bits_per_word));
+    }
+};
+
+template <class _Cp>
+__bit_iterator<_Cp, false>
+rotate(__bit_iterator<_Cp, false> __first, __bit_iterator<_Cp, false> __middle, __bit_iterator<_Cp, false> __last)
+{
+    typedef __bit_iterator<_Cp, false> _I1;
+    typedef  typename _I1::difference_type difference_type;
+    typedef typename _I1::__storage_type __storage_type;
+    difference_type __d1 = __middle - __first;
+    difference_type __d2 = __last - __middle;
+    _I1 __r = __first + __d2;
+    while (__d1 != 0 && __d2 != 0)
+    {
+        if (__d1 <= __d2)
+        {
+            if (__d1 <= __bit_array<_Cp>::capacity())
+            {
+                __bit_array<_Cp> __b(__d1);
+                _VSTD::copy(__first, __middle, __b.begin());
+                _VSTD::copy(__b.begin(), __b.end(), _VSTD::copy(__middle, __last, __first));
+                break;
+            }
+            else
+            {
+                __bit_iterator<_Cp, false> __mp = _VSTD::swap_ranges(__first, __middle, __middle);
+                __first = __middle;
+                __middle = __mp;
+                __d2 -= __d1;
+            }
+        }
+        else
+        {
+            if (__d2 <= __bit_array<_Cp>::capacity())
+            {
+                __bit_array<_Cp> __b(__d2);
+                _VSTD::copy(__middle, __last, __b.begin());
+                _VSTD::copy_backward(__b.begin(), __b.end(), _VSTD::copy_backward(__first, __middle, __last));
+                break;
+            }
+            else
+            {
+                __bit_iterator<_Cp, false> __mp = __first + __d2;
+                _VSTD::swap_ranges(__first, __mp, __middle);
+                __first = __mp;
+                __d1 -= __d2;
+            }
+        }
+    }
+    return __r;
+}
+
+// equal
+
+template <class _Cp, bool _IC1, bool _IC2>
+bool
+__equal_unaligned(__bit_iterator<_Cp, _IC1> __first1, __bit_iterator<_Cp, _IC1> __last1,
+                  __bit_iterator<_Cp, _IC2> __first2)
+{
+    typedef __bit_iterator<_Cp, _IC1> _It;
+    typedef  typename _It::difference_type difference_type;
+    typedef typename _It::__storage_type __storage_type;
+    static const unsigned __bits_per_word = _It::__bits_per_word;
+    difference_type __n = __last1 - __first1;
+    if (__n > 0)
+    {
+        // do first word
+        if (__first1.__ctz_ != 0)
+        {
+            unsigned __clz_f = __bits_per_word - __first1.__ctz_;
+            difference_type __dn = _VSTD::min(static_cast<difference_type>(__clz_f), __n);
+            __n -= __dn;
+            __storage_type __m = (~__storage_type(0) << __first1.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
+            __storage_type __b = *__first1.__seg_ & __m;
+            unsigned __clz_r = __bits_per_word - __first2.__ctz_;
+            __storage_type __ddn = _VSTD::min<__storage_type>(__dn, __clz_r);
+            __m = (~__storage_type(0) << __first2.__ctz_) & (~__storage_type(0) >> (__clz_r - __ddn));
+            if (__first2.__ctz_ > __first1.__ctz_)
+            {
+                if ((*__first2.__seg_ & __m) != (__b << (__first2.__ctz_ - __first1.__ctz_)))
+                    return false;
+            }
+            else
+            {
+                if ((*__first2.__seg_ & __m) != (__b >> (__first1.__ctz_ - __first2.__ctz_)))
+                    return false;
+            }
+            __first2.__seg_ += (__ddn + __first2.__ctz_) / __bits_per_word;
+            __first2.__ctz_ = static_cast<unsigned>((__ddn + __first2.__ctz_)  % __bits_per_word);
+            __dn -= __ddn;
+            if (__dn > 0)
+            {
+                __m = ~__storage_type(0) >> (__bits_per_word - __dn);
+                if ((*__first2.__seg_ & __m) != (__b >> (__first1.__ctz_ + __ddn)))
+                    return false;
+                __first2.__ctz_ = static_cast<unsigned>(__dn);
+            }
+            ++__first1.__seg_;
+            // __first1.__ctz_ = 0;
+        }
+        // __first1.__ctz_ == 0;
+        // do middle words
+        unsigned __clz_r = __bits_per_word - __first2.__ctz_;
+        __storage_type __m = ~__storage_type(0) << __first2.__ctz_;
+        for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first1.__seg_)
+        {
+            __storage_type __b = *__first1.__seg_;
+            if ((*__first2.__seg_ & __m) != (__b << __first2.__ctz_))
+                return false;
+            ++__first2.__seg_;
+            if ((*__first2.__seg_ & ~__m) != (__b >> __clz_r))
+                return false;
+        }
+        // do last word
+        if (__n > 0)
+        {
+            __m = ~__storage_type(0) >> (__bits_per_word - __n);
+            __storage_type __b = *__first1.__seg_ & __m;
+            __storage_type __dn = _VSTD::min(__n, static_cast<difference_type>(__clz_r));
+            __m = (~__storage_type(0) << __first2.__ctz_) & (~__storage_type(0) >> (__clz_r - __dn));
+            if ((*__first2.__seg_ & __m) != (__b << __first2.__ctz_))
+                return false;
+            __first2.__seg_ += (__dn + __first2.__ctz_) / __bits_per_word;
+            __first2.__ctz_ = static_cast<unsigned>((__dn + __first2.__ctz_)  % __bits_per_word);
+            __n -= __dn;
+            if (__n > 0)
+            {
+                __m = ~__storage_type(0) >> (__bits_per_word - __n);
+                if ((*__first2.__seg_ & __m) != (__b >> __dn))
+                    return false;
+            }
+        }
+    }
+    return true;
+}
+
+template <class _Cp, bool _IC1, bool _IC2>
+bool
+__equal_aligned(__bit_iterator<_Cp, _IC1> __first1, __bit_iterator<_Cp, _IC1> __last1,
+                __bit_iterator<_Cp, _IC2> __first2)
+{
+    typedef __bit_iterator<_Cp, _IC1> _It;
+    typedef  typename _It::difference_type difference_type;
+    typedef typename _It::__storage_type __storage_type;
+    static const unsigned __bits_per_word = _It::__bits_per_word;
+    difference_type __n = __last1 - __first1;
+    if (__n > 0)
+    {
+        // do first word
+        if (__first1.__ctz_ != 0)
+        {
+            unsigned __clz = __bits_per_word - __first1.__ctz_;
+            difference_type __dn = _VSTD::min(static_cast<difference_type>(__clz), __n);
+            __n -= __dn;
+            __storage_type __m = (~__storage_type(0) << __first1.__ctz_) & (~__storage_type(0) >> (__clz - __dn));
+            if ((*__first2.__seg_ & __m) != (*__first1.__seg_ & __m))
+                return false;
+            ++__first2.__seg_;
+            ++__first1.__seg_;
+            // __first1.__ctz_ = 0;
+            // __first2.__ctz_ = 0;
+        }
+        // __first1.__ctz_ == 0;
+        // __first2.__ctz_ == 0;
+        // do middle words
+        for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first1.__seg_, ++__first2.__seg_)
+            if (*__first2.__seg_ != *__first1.__seg_)
+                return false;
+        // do last word
+        if (__n > 0)
+        {
+            __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
+            if ((*__first2.__seg_ & __m) != (*__first1.__seg_ & __m))
+                return false;
+        }
+    }
+    return true;
+}
+
+template <class _Cp, bool _IC1, bool _IC2>
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+equal(__bit_iterator<_Cp, _IC1> __first1, __bit_iterator<_Cp, _IC1> __last1, __bit_iterator<_Cp, _IC2> __first2)
+{
+    if (__first1.__ctz_ == __first2.__ctz_)
+        return __equal_aligned(__first1, __last1, __first2);
+    return __equal_unaligned(__first1, __last1, __first2);
+}
+
+template <class _Cp, bool _IsConst,
+          typename _Cp::__storage_type>
+class __bit_iterator
+{
+public:
+    typedef typename _Cp::difference_type                                                          difference_type;
+    typedef bool                                                                                  value_type;
+    typedef __bit_iterator                                                                        pointer;
+    typedef typename conditional<_IsConst, __bit_const_reference<_Cp>, __bit_reference<_Cp> >::type reference;
+    typedef random_access_iterator_tag                                                            iterator_category;
+
+private:
+    typedef typename _Cp::__storage_type                                           __storage_type;
+    typedef typename conditional<_IsConst, typename _Cp::__const_storage_pointer,
+                                           typename _Cp::__storage_pointer>::type  __storage_pointer;
+    static const unsigned __bits_per_word = _Cp::__bits_per_word;
+
+    __storage_pointer __seg_;
+    unsigned          __ctz_;
+
+public:
+    _LIBCPP_INLINE_VISIBILITY __bit_iterator() _NOEXCEPT
+#if _LIBCPP_STD_VER > 11
+    : __seg_(nullptr), __ctz_(0)
+#endif
+    {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    __bit_iterator(const __bit_iterator<_Cp, false>& __it) _NOEXCEPT
+        : __seg_(__it.__seg_), __ctz_(__it.__ctz_) {}
+
+    _LIBCPP_INLINE_VISIBILITY reference operator*() const _NOEXCEPT
+        {return reference(__seg_, __storage_type(1) << __ctz_);}
+
+    _LIBCPP_INLINE_VISIBILITY __bit_iterator& operator++()
+    {
+        if (__ctz_ != __bits_per_word-1)
+            ++__ctz_;
+        else
+        {
+            __ctz_ = 0;
+            ++__seg_;
+        }
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY __bit_iterator operator++(int)
+    {
+        __bit_iterator __tmp = *this;
+        ++(*this);
+        return __tmp;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY __bit_iterator& operator--()
+    {
+        if (__ctz_ != 0)
+            --__ctz_;
+        else
+        {
+            __ctz_ = __bits_per_word - 1;
+            --__seg_;
+        }
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY __bit_iterator operator--(int)
+    {
+        __bit_iterator __tmp = *this;
+        --(*this);
+        return __tmp;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY __bit_iterator& operator+=(difference_type __n)
+    {
+        if (__n >= 0)
+            __seg_ += (__n + __ctz_) / __bits_per_word;
+        else
+            __seg_ += static_cast<difference_type>(__n - __bits_per_word + __ctz_ + 1)
+                    / static_cast<difference_type>(__bits_per_word);
+        __n &= (__bits_per_word - 1);
+        __ctz_ = static_cast<unsigned>((__n + __ctz_)  % __bits_per_word);
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY __bit_iterator& operator-=(difference_type __n)
+    {
+        return *this += -__n;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY __bit_iterator operator+(difference_type __n) const
+    {
+        __bit_iterator __t(*this);
+        __t += __n;
+        return __t;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY __bit_iterator operator-(difference_type __n) const
+    {
+        __bit_iterator __t(*this);
+        __t -= __n;
+        return __t;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    friend __bit_iterator operator+(difference_type __n, const __bit_iterator& __it) {return __it + __n;}
+
+    _LIBCPP_INLINE_VISIBILITY
+    friend difference_type operator-(const __bit_iterator& __x, const __bit_iterator& __y)
+        {return (__x.__seg_ - __y.__seg_) * __bits_per_word + __x.__ctz_ - __y.__ctz_;}
+
+    _LIBCPP_INLINE_VISIBILITY reference operator[](difference_type __n) const {return *(*this + __n);}
+
+    _LIBCPP_INLINE_VISIBILITY friend bool operator==(const __bit_iterator& __x, const __bit_iterator& __y)
+        {return __x.__seg_ == __y.__seg_ && __x.__ctz_ == __y.__ctz_;}
+
+    _LIBCPP_INLINE_VISIBILITY friend bool operator!=(const __bit_iterator& __x, const __bit_iterator& __y)
+        {return !(__x == __y);}
+
+    _LIBCPP_INLINE_VISIBILITY friend bool operator<(const __bit_iterator& __x, const __bit_iterator& __y)
+        {return __x.__seg_ < __y.__seg_ || (__x.__seg_ == __y.__seg_ && __x.__ctz_ < __y.__ctz_);}
+
+    _LIBCPP_INLINE_VISIBILITY friend bool operator>(const __bit_iterator& __x, const __bit_iterator& __y)
+        {return __y < __x;}
+
+    _LIBCPP_INLINE_VISIBILITY friend bool operator<=(const __bit_iterator& __x, const __bit_iterator& __y)
+        {return !(__y < __x);}
+
+    _LIBCPP_INLINE_VISIBILITY friend bool operator>=(const __bit_iterator& __x, const __bit_iterator& __y)
+        {return !(__x < __y);}
+
+private:
+    _LIBCPP_INLINE_VISIBILITY
+    __bit_iterator(__storage_pointer __s, unsigned __ctz) _NOEXCEPT
+        : __seg_(__s), __ctz_(__ctz) {}
+
+#if defined(__clang__) || defined(__IBMCPP__) || defined(_LIBCPP_MSVC)
+    friend typename _Cp::__self;
+#else
+    friend class _Cp::__self;
+#endif
+    friend class __bit_reference<_Cp>;
+    friend class __bit_const_reference<_Cp>;
+    friend class __bit_iterator<_Cp, true>;
+    template <class _Dp> friend struct __bit_array;
+    template <class _Dp> friend void __fill_n_false(__bit_iterator<_Dp, false> __first, typename _Dp::size_type __n);
+    template <class _Dp> friend void __fill_n_true(__bit_iterator<_Dp, false> __first, typename _Dp::size_type __n);
+    template <class _Dp, bool _IC> friend __bit_iterator<_Dp, false> __copy_aligned(__bit_iterator<_Dp, _IC> __first,
+                                                                                  __bit_iterator<_Dp, _IC> __last,
+                                                                                  __bit_iterator<_Dp, false> __result);
+    template <class _Dp, bool _IC> friend __bit_iterator<_Dp, false> __copy_unaligned(__bit_iterator<_Dp, _IC> __first,
+                                                                                    __bit_iterator<_Dp, _IC> __last,
+                                                                                    __bit_iterator<_Dp, false> __result);
+    template <class _Dp, bool _IC> friend __bit_iterator<_Dp, false> copy(__bit_iterator<_Dp, _IC> __first,
+                                                                        __bit_iterator<_Dp, _IC> __last,
+                                                                        __bit_iterator<_Dp, false> __result);
+    template <class _Dp, bool _IC> friend __bit_iterator<_Dp, false> __copy_backward_aligned(__bit_iterator<_Dp, _IC> __first,
+                                                                                           __bit_iterator<_Dp, _IC> __last,
+                                                                                           __bit_iterator<_Dp, false> __result);
+    template <class _Dp, bool _IC> friend __bit_iterator<_Dp, false> __copy_backward_unaligned(__bit_iterator<_Dp, _IC> __first,
+                                                                                             __bit_iterator<_Dp, _IC> __last,
+                                                                                             __bit_iterator<_Dp, false> __result);
+    template <class _Dp, bool _IC> friend __bit_iterator<_Dp, false> copy_backward(__bit_iterator<_Dp, _IC> __first,
+                                                                                 __bit_iterator<_Dp, _IC> __last,
+                                                                                 __bit_iterator<_Dp, false> __result);
+    template <class __C1, class __C2>friend __bit_iterator<__C2, false> __swap_ranges_aligned(__bit_iterator<__C1, false>,
+                                                                                           __bit_iterator<__C1, false>,
+                                                                                           __bit_iterator<__C2, false>);
+    template <class __C1, class __C2>friend __bit_iterator<__C2, false> __swap_ranges_unaligned(__bit_iterator<__C1, false>,
+                                                                                             __bit_iterator<__C1, false>,
+                                                                                             __bit_iterator<__C2, false>);
+    template <class __C1, class __C2>friend __bit_iterator<__C2, false> swap_ranges(__bit_iterator<__C1, false>,
+                                                                                 __bit_iterator<__C1, false>,
+                                                                                 __bit_iterator<__C2, false>);
+    template <class _Dp> friend __bit_iterator<_Dp, false> rotate(__bit_iterator<_Dp, false>,
+                                                                __bit_iterator<_Dp, false>,
+                                                                __bit_iterator<_Dp, false>);
+    template <class _Dp, bool _IC1, bool _IC2> friend bool __equal_aligned(__bit_iterator<_Dp, _IC1>,
+                                                    __bit_iterator<_Dp, _IC1>,
+                                                    __bit_iterator<_Dp, _IC2>);
+    template <class _Dp, bool _IC1, bool _IC2> friend bool __equal_unaligned(__bit_iterator<_Dp, _IC1>,
+                                                      __bit_iterator<_Dp, _IC1>,
+                                                      __bit_iterator<_Dp, _IC2>);
+    template <class _Dp, bool _IC1, bool _IC2> friend bool equal(__bit_iterator<_Dp, _IC1>,
+                                                                __bit_iterator<_Dp, _IC1>,
+                                                                __bit_iterator<_Dp, _IC2>);
+    template <class _Dp, bool _IC> friend __bit_iterator<_Dp, _IC> __find_bool_true(__bit_iterator<_Dp, _IC>,
+                                                                          typename _Dp::size_type);
+    template <class _Dp, bool _IC> friend __bit_iterator<_Dp, _IC> __find_bool_false(__bit_iterator<_Dp, _IC>,
+                                                                           typename _Dp::size_type);
+    template <class _Dp, bool _IC> friend typename __bit_iterator<_Dp, _IC>::difference_type
+                   __count_bool_true(__bit_iterator<_Dp, _IC>, typename _Dp::size_type);
+    template <class _Dp, bool _IC> friend typename __bit_iterator<_Dp, _IC>::difference_type
+                   __count_bool_false(__bit_iterator<_Dp, _IC>, typename _Dp::size_type);
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif  // _LIBCPP___BIT_REFERENCE