Apply @frederick-vs-ja suggestions to support 16-bit platforms

Author: winner245

libcxx/include/bitset

@@ -231,8 +231,14 @@ private:
   void __init(unsigned long long __v, false_type) _NOEXCEPT;
   _LIBCPP_HIDE_FROM_ABI void __init(unsigned long long __v, true_type) _NOEXCEPT;
 #  endif // _LIBCPP_CXX03_LANG
+#  if _LIBCPP_STD_VER == 11
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR void
+  __initialize(unsigned long long __v, size_t __i, size_t __n_words) _NOEXCEPT;
+#  endif // _LIBCPP_STD_VER == 11
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long to_ulong(false_type) const;
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long to_ulong(true_type) const;
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long to_ulong(true_type, false_type) const;
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long to_ulong(true_type, true_type) const;
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long long to_ullong(false_type) const;
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long long to_ullong(true_type) const;
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long long to_ullong(true_type, false_type) const;
@@ -278,23 +284,33 @@ inline _LIBCPP_HIDE_FROM_ABI void __bitset<_N_words, _Size>::__init(unsigned lon
 
 #  endif // _LIBCPP_CXX03_LANG
 
+#  if _LIBCPP_STD_VER == 11
+template <size_t _N_words, size_t _Size>
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR void
+__bitset<_N_words, _Size>::__initialize(unsigned long long __v, size_t __i, size_t __n_words) _NOEXCEPT {
+  if (__i < __n_words) {
+    __first_[__i] = static_cast<__storage_type>(__v >> __bits_per_word * __i);
+    __initialize(__v, __i + 1, __n_words);
+  }
+}
+#  endif
+
 template <size_t _N_words, size_t _Size>
 inline _LIBCPP_CONSTEXPR __bitset<_N_words, _Size>::__bitset(unsigned long long __v) _NOEXCEPT
 #  ifndef _LIBCPP_CXX03_LANG
-#    if __SIZEOF_SIZE_T__ == 8
-    : __first_{__v}
-#    elif __SIZEOF_SIZE_T__ == 4
-    : __first_{static_cast<__storage_type>(__v),
-               _Size >= 2 * __bits_per_word
-                   ? static_cast<__storage_type>(__v >> __bits_per_word)
-                   : static_cast<__storage_type>((__v >> __bits_per_word) &
-                                                 (__storage_type(1) << (_Size - __bits_per_word)) - 1)}
-#    else
-#      error This constructor has not been ported to this platform
-#    endif
+    : __first_{static_cast<__storage_type>(__v)}
 #  endif
 {
-#  ifdef _LIBCPP_CXX03_LANG
+#  ifndef _LIBCPP_CXX03_LANG
+  const size_t __ull_words = sizeof(unsigned long long) / sizeof(__storage_type);
+  const size_t __n_words   = _N_words < __ull_words ? _N_words : __ull_words;
+#    if _LIBCPP_STD_VER >= 14
+  for (size_t __i = 1; __i < __n_words; ++__i)
+    __first_[__i] = static_cast<__storage_type>(__v >> __bits_per_word * __i);
+#    else
+  __initialize(__v, 1, __n_words);
+#    endif
+#  else
   __init(__v, integral_constant<bool, sizeof(unsigned long long) == sizeof(__storage_type)>());
 #  endif
 }
@@ -344,13 +360,33 @@ __bitset<_N_words, _Size>::to_ulong(false_type) const {
   if (__i != __e)
     __throw_overflow_error("bitset to_ulong overflow error");
 
-  return __first_[0];
+  return to_ulong(true_type());
 }
 
 template <size_t _N_words, size_t _Size>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long
 __bitset<_N_words, _Size>::to_ulong(true_type) const {
-  return __first_[0];
+  return to_ulong(true_type(), integral_constant<bool, sizeof(__storage_type) < sizeof(unsigned long)>());
+}
+
+template <size_t _N_words, size_t _Size>
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long
+__bitset<_N_words, _Size>::to_ulong(true_type, false_type) const {
+  return static_cast<unsigned long>(__first_[0]);
+}
+
+template <size_t _N_words, size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long
+__bitset<_N_words, _Size>::to_ulong(true_type, true_type) const {
+  unsigned long __r = __first_[0];
+  _LIBCPP_DIAGNOSTIC_PUSH
+  _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wshift-count-overflow")
+  const size_t __ul_words = sizeof(unsigned long) / sizeof(__storage_type);
+  const size_t __n_words  = _N_words < __ul_words ? _N_words : __ul_words;
+  for (size_t __i = 1; __i < __n_words; ++__i)
+    __r |= static_cast<unsigned long>(__first_[__i]) << (__bits_per_word * __i);
+  _LIBCPP_DIAGNOSTIC_POP
+  return __r;
 }
 
 template <size_t _N_words, size_t _Size>
@@ -373,7 +409,7 @@ __bitset<_N_words, _Size>::to_ullong(true_type) const {
 template <size_t _N_words, size_t _Size>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long long
 __bitset<_N_words, _Size>::to_ullong(true_type, false_type) const {
-  return __first_[0];
+  return static_cast<unsigned long long>(__first_[0]);
 }
 
 template <size_t _N_words, size_t _Size>
@@ -383,9 +419,9 @@ __bitset<_N_words, _Size>::to_ullong(true_type, true_type) const {
   _LIBCPP_DIAGNOSTIC_PUSH
   _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wshift-count-overflow")
   const size_t __ull_words = sizeof(unsigned long long) / sizeof(__storage_type);
-  const size_t __n_words = _N_words < __ull_words ? _N_words : __ull_words;
+  const size_t __n_words   = _N_words < __ull_words ? _N_words : __ull_words;
   for (size_t __i = 1; __i < __n_words; ++__i)
-    __r |= static_cast<unsigned long long>(__first_[__i]) << (sizeof(__storage_type) * CHAR_BIT * __i);
+    __r |= static_cast<unsigned long long>(__first_[__i]) << (__bits_per_word * __i);
   _LIBCPP_DIAGNOSTIC_POP
   return __r;
 }
@@ -494,8 +530,7 @@ inline _LIBCPP_CONSTEXPR __bitset<1, _Size>::__bitset() _NOEXCEPT : __first_(0)
 
 template <size_t _Size>
 inline _LIBCPP_CONSTEXPR __bitset<1, _Size>::__bitset(unsigned long long __v) _NOEXCEPT
-    : __first_(_Size == __bits_per_word ? static_cast<__storage_type>(__v)
-                                        : static_cast<__storage_type>(__v) & ((__storage_type(1) << _Size) - 1)) {}
+    : __first_(static_cast<__storage_type>(__v)) {}
 
 template <size_t _Size>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 void
@@ -524,12 +559,12 @@ inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 void __bitset<1, _Siz
 
 template <size_t _Size>
 inline _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long __bitset<1, _Size>::to_ulong() const {
-  return __first_;
+  return static_cast<unsigned long>(__first_);
 }
 
 template <size_t _Size>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long long __bitset<1, _Size>::to_ullong() const {
-  return __first_;
+  return static_cast<unsigned long long>(__first_);
 }
 
 template <size_t _Size>
@@ -595,8 +630,8 @@ protected:
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 void flip() _NOEXCEPT {}
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long to_ulong() const { return 0; }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long long to_ullong() const { return 0; }
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long to_ulong() const { return 0UL; }
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long long to_ullong() const { return 0ULL; }
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool all() const _NOEXCEPT { return true; }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool any() const _NOEXCEPT { return false; }
@@ -626,7 +661,8 @@ public:
 
   // 23.3.5.1 constructors:
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bitset() _NOEXCEPT {}
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bitset(unsigned long long __v) _NOEXCEPT : __base(__v) {}
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bitset(unsigned long long __v) _NOEXCEPT
+      : __base(sizeof(unsigned long long) * CHAR_BIT <= _Size ? __v : __v & (1ULL << _Size) - 1) {}
   template <class _CharT, __enable_if_t<_IsCharLikeType<_CharT>::value, int> = 0>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 explicit bitset(
       const _CharT* __str,