Simplify flip() for std::bit_set

Author: winner245

libcxx/include/bitset

@@ -319,18 +319,8 @@ __bitset<_N_words, _Size>::operator^=(const __bitset& __v) _NOEXCEPT {
 
 template <size_t _N_words, size_t _Size>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 void __bitset<_N_words, _Size>::flip() _NOEXCEPT {
-  // do middle whole words
-  size_type __n         = _Size;
-  __storage_pointer __p = __first_;
-  for (; __n >= __bits_per_word; ++__p, __n -= __bits_per_word)
-    *__p = ~*__p;
-  // do last partial word
-  if (__n > 0) {
-    __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
-    __storage_type __b = *__p & __m;
-    *__p &= ~__m;
-    *__p |= ~__b & __m;
-  }
+  for (size_type __i = 0; __i < _N_words; ++__i)
+    __first_[__i] = ~__first_[__i];
 }
 
 template <size_t _N_words, size_t _Size>