[libc++] Implement P2417R2 (A more constexpr bitset)

Reviewed By: ldionne, #libc

Spies: jloser, arichardson, libcxx-commits, arphaman

Differential Revision: https://reviews.llvm.org/D131218

1 files changed, 155 insertions, 115 deletions

diff --git a/libcxx/include/bitset b/libcxx/include/bitset
index 67760a7..ea6ced6 100644
--- a/libcxx/include/bitset
+++ b/libcxx/include/bitset
@@ -42,61 +42,61 @@ public:
     template <class charT>
         explicit bitset(const charT* str,
                         typename basic_string<charT>::size_type n = basic_string<charT>::npos,
-                        charT zero = charT('0'), charT one = charT('1'));
+                        charT zero = charT('0'), charT one = charT('1')); // constexpr since C++23
     template<class charT, class traits, class Allocator>
         explicit bitset(const basic_string<charT,traits,Allocator>& str,
                         typename basic_string<charT,traits,Allocator>::size_type pos = 0,
                         typename basic_string<charT,traits,Allocator>::size_type n =
                                  basic_string<charT,traits,Allocator>::npos,
-                        charT zero = charT('0'), charT one = charT('1'));
+                        charT zero = charT('0'), charT one = charT('1')); // constexpr since C++23
 
     // 23.3.5.2 bitset operations:
-    bitset& operator&=(const bitset& rhs) noexcept;
-    bitset& operator|=(const bitset& rhs) noexcept;
-    bitset& operator^=(const bitset& rhs) noexcept;
-    bitset& operator<<=(size_t pos) noexcept;
-    bitset& operator>>=(size_t pos) noexcept;
-    bitset& set() noexcept;
-    bitset& set(size_t pos, bool val = true);
-    bitset& reset() noexcept;
-    bitset& reset(size_t pos);
-    bitset operator~() const noexcept;
-    bitset& flip() noexcept;
-    bitset& flip(size_t pos);
+    bitset& operator&=(const bitset& rhs) noexcept; // constexpr since C++23
+    bitset& operator|=(const bitset& rhs) noexcept; // constexpr since C++23
+    bitset& operator^=(const bitset& rhs) noexcept; // constexpr since C++23
+    bitset& operator<<=(size_t pos) noexcept;       // constexpr since C++23
+    bitset& operator>>=(size_t pos) noexcept;       // constexpr since C++23
+    bitset& set() noexcept;                         // constexpr since C++23
+    bitset& set(size_t pos, bool val = true);       // constexpr since C++23
+    bitset& reset() noexcept;                       // constexpr since C++23
+    bitset& reset(size_t pos);                      // constexpr since C++23
+    bitset operator~() const noexcept;              // constexpr since C++23
+    bitset& flip() noexcept;                        // constexpr since C++23
+    bitset& flip(size_t pos);                       // constexpr since C++23
 
     // element access:
-    constexpr bool operator[](size_t pos) const; // for b[i];
-    reference operator[](size_t pos);            // for b[i];
-    unsigned long to_ulong() const;
-    unsigned long long to_ullong() const;
-    template <class charT, class traits, class Allocator>
+    constexpr bool operator[](size_t pos) const;
+    reference operator[](size_t pos);            // constexpr since C++23
+    unsigned long to_ulong() const;              // constexpr since C++23
+    unsigned long long to_ullong() const;        // constexpr since C++23
+    template <class charT, class traits, class Allocator> // constexpr since C++23
         basic_string<charT, traits, Allocator> to_string(charT zero = charT('0'), charT one = charT('1')) const;
-    template <class charT, class traits>
+    template <class charT, class traits> // constexpr since C++23
         basic_string<charT, traits, allocator<charT> > to_string(charT zero = charT('0'), charT one = charT('1')) const;
-    template <class charT>
+    template <class charT> // constexpr since C++23
         basic_string<charT, char_traits<charT>, allocator<charT> > to_string(charT zero = charT('0'), charT one = charT('1')) const;
-    basic_string<char, char_traits<char>, allocator<char> > to_string(char zero = '0', char one = '1') const;
-    size_t count() const noexcept;
-    constexpr size_t size() const noexcept;
-    bool operator==(const bitset& rhs) const noexcept;
-    bool operator!=(const bitset& rhs) const noexcept;
-    bool test(size_t pos) const;
-    bool all() const noexcept;
-    bool any() const noexcept;
-    bool none() const noexcept;
-    bitset operator<<(size_t pos) const noexcept;
-    bitset operator>>(size_t pos) const noexcept;
+    basic_string<char, char_traits<char>, allocator<char> > to_string(char zero = '0', char one = '1') const; // constexpr since C++23
+    size_t count() const noexcept;                     // constexpr since C++23
+    constexpr size_t size() const noexcept;            // constexpr since C++23
+    bool operator==(const bitset& rhs) const noexcept; // constexpr since C++23
+    bool operator!=(const bitset& rhs) const noexcept; // constexpr since C++23
+    bool test(size_t pos) const;                       // constexpr since C++23
+    bool all() const noexcept;                         // constexpr since C++23
+    bool any() const noexcept;                         // constexpr since C++23
+    bool none() const noexcept;                        // constexpr since C++23
+    bitset<N> operator<<(size_t pos) const noexcept;   // constexpr since C++23
+    bitset<N> operator>>(size_t pos) const noexcept;   // constexpr since C++23
 };
 
 // 23.3.5.3 bitset operators:
 template <size_t N>
-bitset<N> operator&(const bitset<N>&, const bitset<N>&) noexcept;
+bitset<N> operator&(const bitset<N>&, const bitset<N>&) noexcept; // constexpr since C++23
 
 template <size_t N>
-bitset<N> operator|(const bitset<N>&, const bitset<N>&) noexcept;
+bitset<N> operator|(const bitset<N>&, const bitset<N>&) noexcept; // constexpr since C++23
 
 template <size_t N>
-bitset<N> operator^(const bitset<N>&, const bitset<N>&) noexcept;
+bitset<N> operator^(const bitset<N>&, const bitset<N>&) noexcept; // constexpr since C++23
 
 template <class charT, class traits, size_t N>
 basic_istream<charT, traits>&
@@ -178,30 +178,30 @@ protected:
     _LIBCPP_INLINE_VISIBILITY
     explicit _LIBCPP_CONSTEXPR __bitset(unsigned long long __v) _NOEXCEPT;
 
-    _LIBCPP_INLINE_VISIBILITY reference __make_ref(size_t __pos) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 reference __make_ref(size_t __pos) _NOEXCEPT
         {return reference(__first_ + __pos / __bits_per_word, __storage_type(1) << __pos % __bits_per_word);}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR const_reference __make_ref(size_t __pos) const _NOEXCEPT
         {return const_reference(__first_ + __pos / __bits_per_word, __storage_type(1) << __pos % __bits_per_word);}
-    _LIBCPP_INLINE_VISIBILITY iterator __make_iter(size_t __pos) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 iterator __make_iter(size_t __pos) _NOEXCEPT
         {return iterator(__first_ + __pos / __bits_per_word, __pos % __bits_per_word);}
-    _LIBCPP_INLINE_VISIBILITY const_iterator __make_iter(size_t __pos) const _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 const_iterator __make_iter(size_t __pos) const _NOEXCEPT
         {return const_iterator(__first_ + __pos / __bits_per_word, __pos % __bits_per_word);}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void operator&=(const __bitset& __v) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void operator|=(const __bitset& __v) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void operator^=(const __bitset& __v) _NOEXCEPT;
 
-    void flip() _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY unsigned long to_ulong() const
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void flip() _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long to_ulong() const
         {return to_ulong(integral_constant<bool, _Size < sizeof(unsigned long) * CHAR_BIT>());}
-    _LIBCPP_INLINE_VISIBILITY unsigned long long to_ullong() const
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long to_ullong() const
         {return to_ullong(integral_constant<bool, _Size < sizeof(unsigned long long) * CHAR_BIT>());}
 
-    bool all() const _NOEXCEPT;
-    bool any() const _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 bool all() const _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 bool any() const _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     size_t __hash_code() const _NOEXCEPT;
 private:
@@ -210,14 +210,17 @@ private:
     _LIBCPP_INLINE_VISIBILITY
     void __init(unsigned long long __v, true_type) _NOEXCEPT;
 #endif // _LIBCPP_CXX03_LANG
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long to_ulong(false_type) const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long to_ulong(true_type) const;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long long to_ullong(false_type) const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long long to_ullong(true_type) const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long long to_ullong(true_type, false_type) const;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long long to_ullong(true_type, true_type) const;
 };
 
@@ -290,7 +293,7 @@ __bitset<_N_words, _Size>::__bitset(unsigned long long __v) _NOEXCEPT
 
 template <size_t _N_words, size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<_N_words, _Size>::operator&=(const __bitset& __v) _NOEXCEPT
 {
     for (size_type __i = 0; __i < _N_words; ++__i)
@@ -299,7 +302,7 @@ __bitset<_N_words, _Size>::operator&=(const __bitset& __v) _NOEXCEPT
 
 template <size_t _N_words, size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<_N_words, _Size>::operator|=(const __bitset& __v) _NOEXCEPT
 {
     for (size_type __i = 0; __i < _N_words; ++__i)
@@ -308,7 +311,7 @@ __bitset<_N_words, _Size>::operator|=(const __bitset& __v) _NOEXCEPT
 
 template <size_t _N_words, size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<_N_words, _Size>::operator^=(const __bitset& __v) _NOEXCEPT
 {
     for (size_type __i = 0; __i < _N_words; ++__i)
@@ -316,7 +319,7 @@ __bitset<_N_words, _Size>::operator^=(const __bitset& __v) _NOEXCEPT
 }
 
 template <size_t _N_words, size_t _Size>
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<_N_words, _Size>::flip() _NOEXCEPT
 {
     // do middle whole words
@@ -335,7 +338,7 @@ __bitset<_N_words, _Size>::flip() _NOEXCEPT
 }
 
 template <size_t _N_words, size_t _Size>
-unsigned long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long
 __bitset<_N_words, _Size>::to_ulong(false_type) const
 {
     const_iterator __e = __make_iter(_Size);
@@ -348,14 +351,14 @@ __bitset<_N_words, _Size>::to_ulong(false_type) const
 
 template <size_t _N_words, size_t _Size>
 inline
-unsigned long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long
 __bitset<_N_words, _Size>::to_ulong(true_type) const
 {
     return __first_[0];
 }
 
 template <size_t _N_words, size_t _Size>
-unsigned long long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long
 __bitset<_N_words, _Size>::to_ullong(false_type) const
 {
     const_iterator __e = __make_iter(_Size);
@@ -368,7 +371,7 @@ __bitset<_N_words, _Size>::to_ullong(false_type) const
 
 template <size_t _N_words, size_t _Size>
 inline
-unsigned long long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long
 __bitset<_N_words, _Size>::to_ullong(true_type) const
 {
     return to_ullong(true_type(), integral_constant<bool, sizeof(__storage_type) < sizeof(unsigned long long)>());
@@ -376,14 +379,14 @@ __bitset<_N_words, _Size>::to_ullong(true_type) const
 
 template <size_t _N_words, size_t _Size>
 inline
-unsigned long long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long
 __bitset<_N_words, _Size>::to_ullong(true_type, false_type) const
 {
     return __first_[0];
 }
 
 template <size_t _N_words, size_t _Size>
-unsigned long long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long
 __bitset<_N_words, _Size>::to_ullong(true_type, true_type) const
 {
     unsigned long long __r = __first_[0];
@@ -393,7 +396,7 @@ __bitset<_N_words, _Size>::to_ullong(true_type, true_type) const
 }
 
 template <size_t _N_words, size_t _Size>
-bool
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 bool
 __bitset<_N_words, _Size>::all() const _NOEXCEPT
 {
     // do middle whole words
@@ -413,7 +416,7 @@ __bitset<_N_words, _Size>::all() const _NOEXCEPT
 }
 
 template <size_t _N_words, size_t _Size>
-bool
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 bool
 __bitset<_N_words, _Size>::any() const _NOEXCEPT
 {
     // do middle whole words
@@ -474,33 +477,33 @@ protected:
     _LIBCPP_INLINE_VISIBILITY
     explicit _LIBCPP_CONSTEXPR __bitset(unsigned long long __v) _NOEXCEPT;
 
-    _LIBCPP_INLINE_VISIBILITY reference __make_ref(size_t __pos) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 reference __make_ref(size_t __pos) _NOEXCEPT
         {return reference(&__first_, __storage_type(1) << __pos);}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR const_reference __make_ref(size_t __pos) const _NOEXCEPT
         {return const_reference(&__first_, __storage_type(1) << __pos);}
-    _LIBCPP_INLINE_VISIBILITY iterator __make_iter(size_t __pos) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 iterator __make_iter(size_t __pos) _NOEXCEPT
         {return iterator(&__first_ + __pos / __bits_per_word, __pos % __bits_per_word);}
-    _LIBCPP_INLINE_VISIBILITY const_iterator __make_iter(size_t __pos) const _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 const_iterator __make_iter(size_t __pos) const _NOEXCEPT
         {return const_iterator(&__first_ + __pos / __bits_per_word, __pos % __bits_per_word);}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void operator&=(const __bitset& __v) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void operator|=(const __bitset& __v) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void operator^=(const __bitset& __v) _NOEXCEPT;
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void flip() _NOEXCEPT;
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long to_ulong() const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long long to_ullong() const;
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool all() const _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool any() const _NOEXCEPT;
 
     _LIBCPP_INLINE_VISIBILITY
@@ -528,7 +531,7 @@ __bitset<1, _Size>::__bitset(unsigned long long __v) _NOEXCEPT
 
 template <size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<1, _Size>::operator&=(const __bitset& __v) _NOEXCEPT
 {
     __first_ &= __v.__first_;
@@ -536,7 +539,7 @@ __bitset<1, _Size>::operator&=(const __bitset& __v) _NOEXCEPT
 
 template <size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<1, _Size>::operator|=(const __bitset& __v) _NOEXCEPT
 {
     __first_ |= __v.__first_;
@@ -544,7 +547,7 @@ __bitset<1, _Size>::operator|=(const __bitset& __v) _NOEXCEPT
 
 template <size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<1, _Size>::operator^=(const __bitset& __v) _NOEXCEPT
 {
     __first_ ^= __v.__first_;
@@ -552,7 +555,7 @@ __bitset<1, _Size>::operator^=(const __bitset& __v) _NOEXCEPT
 
 template <size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<1, _Size>::flip() _NOEXCEPT
 {
     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - _Size);
@@ -562,7 +565,7 @@ __bitset<1, _Size>::flip() _NOEXCEPT
 
 template <size_t _Size>
 inline
-unsigned long
+_LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long
 __bitset<1, _Size>::to_ulong() const
 {
     return __first_;
@@ -570,7 +573,7 @@ __bitset<1, _Size>::to_ulong() const
 
 template <size_t _Size>
 inline
-unsigned long long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long
 __bitset<1, _Size>::to_ullong() const
 {
     return __first_;
@@ -578,7 +581,7 @@ __bitset<1, _Size>::to_ullong() const
 
 template <size_t _Size>
 inline
-bool
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 bool
 __bitset<1, _Size>::all() const _NOEXCEPT
 {
     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - _Size);
@@ -587,7 +590,7 @@ __bitset<1, _Size>::all() const _NOEXCEPT
 
 template <size_t _Size>
 inline
-bool
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 bool
 __bitset<1, _Size>::any() const _NOEXCEPT
 {
     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - _Size);
@@ -631,26 +634,26 @@ protected:
     _LIBCPP_INLINE_VISIBILITY
     explicit _LIBCPP_CONSTEXPR __bitset(unsigned long long) _NOEXCEPT;
 
-    _LIBCPP_INLINE_VISIBILITY reference __make_ref(size_t) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 reference __make_ref(size_t) _NOEXCEPT
         {return reference(nullptr, 1);}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR const_reference __make_ref(size_t) const _NOEXCEPT
         {return const_reference(nullptr, 1);}
-    _LIBCPP_INLINE_VISIBILITY iterator __make_iter(size_t) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 iterator __make_iter(size_t) _NOEXCEPT
         {return iterator(nullptr, 0);}
-    _LIBCPP_INLINE_VISIBILITY const_iterator __make_iter(size_t) const _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 const_iterator __make_iter(size_t) const _NOEXCEPT
         {return const_iterator(nullptr, 0);}
 
-    _LIBCPP_INLINE_VISIBILITY void operator&=(const __bitset&) _NOEXCEPT {}
-    _LIBCPP_INLINE_VISIBILITY void operator|=(const __bitset&) _NOEXCEPT {}
-    _LIBCPP_INLINE_VISIBILITY void operator^=(const __bitset&) _NOEXCEPT {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 void operator&=(const __bitset&) _NOEXCEPT {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 void operator|=(const __bitset&) _NOEXCEPT {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 void operator^=(const __bitset&) _NOEXCEPT {}
 
-    _LIBCPP_INLINE_VISIBILITY void flip() _NOEXCEPT {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 void flip() _NOEXCEPT {}
 
-    _LIBCPP_INLINE_VISIBILITY unsigned long to_ulong() const {return 0;}
-    _LIBCPP_INLINE_VISIBILITY unsigned long long to_ullong() const {return 0;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long to_ulong() const {return 0;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long to_ullong() const {return 0;}
 
-    _LIBCPP_INLINE_VISIBILITY bool all() const _NOEXCEPT {return true;}
-    _LIBCPP_INLINE_VISIBILITY bool any() const _NOEXCEPT {return false;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 bool all() const _NOEXCEPT {return true;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 bool any() const _NOEXCEPT {return false;}
 
     _LIBCPP_INLINE_VISIBILITY size_t __hash_code() const _NOEXCEPT {return 0;}
 };
@@ -687,10 +690,12 @@ public:
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
         bitset(unsigned long long __v) _NOEXCEPT : base(__v) {}
     template<class _CharT, class = __enable_if_t<_IsCharLikeType<_CharT>::value> >
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
         explicit bitset(const _CharT* __str,
                         typename basic_string<_CharT>::size_type __n = basic_string<_CharT>::npos,
                         _CharT __zero = _CharT('0'), _CharT __one = _CharT('1'));
     template<class _CharT, class _Traits, class _Allocator>
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
         explicit bitset(const basic_string<_CharT,_Traits,_Allocator>& __str,
                         typename basic_string<_CharT,_Traits,_Allocator>::size_type __pos = 0,
                         typename basic_string<_CharT,_Traits,_Allocator>::size_type __n =
@@ -698,24 +703,29 @@ public:
                         _CharT __zero = _CharT('0'), _CharT __one = _CharT('1'));
 
     // 23.3.5.2 bitset operations:
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& operator&=(const bitset& __rhs) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& operator|=(const bitset& __rhs) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& operator^=(const bitset& __rhs) _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& operator<<=(size_t __pos) _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& operator>>=(size_t __pos) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& set() _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& set(size_t __pos, bool __val = true);
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& reset() _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& reset(size_t __pos);
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset  operator~() const _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& flip() _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& flip(size_t __pos);
 
     // element access:
@@ -724,41 +734,43 @@ public:
 #else
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const_reference operator[](size_t __p) const {return base::__make_ref(__p);}
 #endif
-    _LIBCPP_HIDE_FROM_ABI                         reference operator[](size_t __p)       {return base::__make_ref(__p);}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 reference operator[](size_t __p)       {return base::__make_ref(__p);}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long to_ulong() const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long long to_ullong() const;
     template <class _CharT, class _Traits, class _Allocator>
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
         basic_string<_CharT, _Traits, _Allocator> to_string(_CharT __zero = _CharT('0'),
                                                             _CharT __one = _CharT('1')) const;
     template <class _CharT, class _Traits>
-        _LIBCPP_INLINE_VISIBILITY
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
         basic_string<_CharT, _Traits, allocator<_CharT> > to_string(_CharT __zero = _CharT('0'),
                                                                     _CharT __one = _CharT('1')) const;
     template <class _CharT>
-        _LIBCPP_INLINE_VISIBILITY
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
         basic_string<_CharT, char_traits<_CharT>, allocator<_CharT> > to_string(_CharT __zero = _CharT('0'),
                                                                                 _CharT __one = _CharT('1')) const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     basic_string<char, char_traits<char>, allocator<char> > to_string(char __zero = '0',
                                                                       char __one = '1') const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     size_t count() const _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR size_t size() const _NOEXCEPT {return _Size;}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool operator==(const bitset& __rhs) const _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool operator!=(const bitset& __rhs) const _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool test(size_t __pos) const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool all() const _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool any() const _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY bool none() const _NOEXCEPT {return !any();}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 bool none() const _NOEXCEPT {return !any();}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset operator<<(size_t __pos) const _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset operator>>(size_t __pos) const _NOEXCEPT;
 
 private:
@@ -771,6 +783,7 @@ private:
 
 template <size_t _Size>
 template<class _CharT, class>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>::bitset(const _CharT* __str,
                       typename basic_string<_CharT>::size_type __n,
                       _CharT __zero, _CharT __one)
@@ -792,6 +805,7 @@ bitset<_Size>::bitset(const _CharT* __str,
 
 template <size_t _Size>
 template<class _CharT, class _Traits, class _Allocator>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>::bitset(const basic_string<_CharT,_Traits,_Allocator>& __str,
        typename basic_string<_CharT,_Traits,_Allocator>::size_type __pos,
        typename basic_string<_CharT,_Traits,_Allocator>::size_type __n,
@@ -817,6 +831,7 @@ bitset<_Size>::bitset(const basic_string<_CharT,_Traits,_Allocator>& __str,
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::operator&=(const bitset& __rhs) _NOEXCEPT
 {
@@ -826,6 +841,7 @@ bitset<_Size>::operator&=(const bitset& __rhs) _NOEXCEPT
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::operator|=(const bitset& __rhs) _NOEXCEPT
 {
@@ -835,6 +851,7 @@ bitset<_Size>::operator|=(const bitset& __rhs) _NOEXCEPT
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::operator^=(const bitset& __rhs) _NOEXCEPT
 {
@@ -843,6 +860,7 @@ bitset<_Size>::operator^=(const bitset& __rhs) _NOEXCEPT
 }
 
 template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::operator<<=(size_t __pos) _NOEXCEPT
 {
@@ -853,6 +871,7 @@ bitset<_Size>::operator<<=(size_t __pos) _NOEXCEPT
 }
 
 template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::operator>>=(size_t __pos) _NOEXCEPT
 {
@@ -864,6 +883,7 @@ bitset<_Size>::operator>>=(size_t __pos) _NOEXCEPT
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::set() _NOEXCEPT
 {
@@ -872,6 +892,7 @@ bitset<_Size>::set() _NOEXCEPT
 }
 
 template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::set(size_t __pos, bool __val)
 {
@@ -884,6 +905,7 @@ bitset<_Size>::set(size_t __pos, bool __val)
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::reset() _NOEXCEPT
 {
@@ -892,6 +914,7 @@ bitset<_Size>::reset() _NOEXCEPT
 }
 
 template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::reset(size_t __pos)
 {
@@ -904,6 +927,7 @@ bitset<_Size>::reset(size_t __pos)
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>
 bitset<_Size>::operator~() const _NOEXCEPT
 {
@@ -914,6 +938,7 @@ bitset<_Size>::operator~() const _NOEXCEPT
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::flip() _NOEXCEPT
 {
@@ -922,6 +947,7 @@ bitset<_Size>::flip() _NOEXCEPT
 }
 
 template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::flip(size_t __pos)
 {
@@ -935,6 +961,7 @@ bitset<_Size>::flip(size_t __pos)
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 unsigned long
 bitset<_Size>::to_ulong() const
 {
@@ -943,6 +970,7 @@ bitset<_Size>::to_ulong() const
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 unsigned long long
 bitset<_Size>::to_ullong() const
 {
@@ -951,6 +979,7 @@ bitset<_Size>::to_ullong() const
 
 template <size_t _Size>
 template <class _CharT, class _Traits, class _Allocator>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 basic_string<_CharT, _Traits, _Allocator>
 bitset<_Size>::to_string(_CharT __zero, _CharT __one) const
 {
@@ -966,6 +995,7 @@ bitset<_Size>::to_string(_CharT __zero, _CharT __one) const
 template <size_t _Size>
 template <class _CharT, class _Traits>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 basic_string<_CharT, _Traits, allocator<_CharT> >
 bitset<_Size>::to_string(_CharT __zero, _CharT __one) const
 {
@@ -975,6 +1005,7 @@ bitset<_Size>::to_string(_CharT __zero, _CharT __one) const
 template <size_t _Size>
 template <class _CharT>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 basic_string<_CharT, char_traits<_CharT>, allocator<_CharT> >
 bitset<_Size>::to_string(_CharT __zero, _CharT __one) const
 {
@@ -983,6 +1014,7 @@ bitset<_Size>::to_string(_CharT __zero, _CharT __one) const
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 basic_string<char, char_traits<char>, allocator<char> >
 bitset<_Size>::to_string(char __zero, char __one) const
 {
@@ -991,6 +1023,7 @@ bitset<_Size>::to_string(char __zero, char __one) const
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 size_t
 bitset<_Size>::count() const _NOEXCEPT
 {
@@ -999,6 +1032,7 @@ bitset<_Size>::count() const _NOEXCEPT
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bool
 bitset<_Size>::operator==(const bitset& __rhs) const _NOEXCEPT
 {
@@ -1007,6 +1041,7 @@ bitset<_Size>::operator==(const bitset& __rhs) const _NOEXCEPT
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bool
 bitset<_Size>::operator!=(const bitset& __rhs) const _NOEXCEPT
 {
@@ -1014,6 +1049,7 @@ bitset<_Size>::operator!=(const bitset& __rhs) const _NOEXCEPT
 }
 
 template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bool
 bitset<_Size>::test(size_t __pos) const
 {
@@ -1025,6 +1061,7 @@ bitset<_Size>::test(size_t __pos) const
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bool
 bitset<_Size>::all() const _NOEXCEPT
 {
@@ -1033,6 +1070,7 @@ bitset<_Size>::all() const _NOEXCEPT
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bool
 bitset<_Size>::any() const _NOEXCEPT
 {
@@ -1041,6 +1079,7 @@ bitset<_Size>::any() const _NOEXCEPT
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>
 bitset<_Size>::operator<<(size_t __pos) const _NOEXCEPT
 {
@@ -1051,6 +1090,7 @@ bitset<_Size>::operator<<(size_t __pos) const _NOEXCEPT
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>
 bitset<_Size>::operator>>(size_t __pos) const _NOEXCEPT
 {
@@ -1060,7 +1100,7 @@ bitset<_Size>::operator>>(size_t __pos) const _NOEXCEPT
 }
 
 template <size_t _Size>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>
 operator&(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT
 {
@@ -1070,7 +1110,7 @@ operator&(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT
 }
 
 template <size_t _Size>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>
 operator|(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT
 {
@@ -1080,7 +1120,7 @@ operator|(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT
 }
 
 template <size_t _Size>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>
 operator^(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT
 {