[libc++] Remove redundant assignments in bitset string-like constructors

[winner245]

The following three string-like constructors for std::bitset

• bitset(const CharT* str, std::size_t n, CharT zero, CharT one);
• bitset(const std::basic_string<CharT, Traits, Alloc>& str, typename std::basic_string<CharT, Traits, Alloc>::size_type pos, CharT zero, CharT one);
• bitset(std::basic_string_view<CharT, Traits> str, std::size_t pos, std::size_t n, CharT zero, CharT one)

already initialize the underlying storage array to all zeroes via default-constructor of the base class __bitset. Therefore, re-assigning the storage array to zeroes via std::fill_n in the string-like constructors is truly redundant.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Peng Liu (winner245)

Changes

The following three string-like constructors for std::bitset

• bitset(const CharT* str, std::size_t n, CharT zero, CharT one);
• bitset(const std::basic_string<CharT, Traits, Alloc>& str, typename std::basic_string<CharT, Traits, Alloc>::size_type pos, CharT zero, CharT one);
• bitset(std::basic_string_view<CharT, Traits> str, std::size_t pos, std::size_t n, CharT zero, CharT one)

already initialize the underlying storage array to all zeroes via default-constructor of the base class __bitset. Therefore, re-assigning the storage array to zeroes via std::fill_n in the string-like constructors is truly redundant.

---

Full diff: https://github.com/llvm/llvm-project/pull/121424.diff

1 Files Affected:

• (modified) libcxx/include/bitset (-1)

diff --git a/libcxx/include/bitset b/libcxx/include/bitset
index a20842985b3d5..3cd4312e0171d 100644
--- a/libcxx/include/bitset
+++ b/libcxx/include/bitset
@@ -736,7 +736,6 @@ private:
       _CharT __c   = __str[__mp - 1 - __i];
       (*this)[__i] = _Traits::eq(__c, __one);
     }
-    std::fill(__base::__make_iter(__i), __base::__make_iter(_Size), false);
   }
 
   _LIBCPP_HIDE_FROM_ABI size_t __hash_code() const _NOEXCEPT { return __base::__hash_code(); }