Author: ericwf Date: Thu Aug 27 22:02:37 2015 New Revision: 246266 URL: http://llvm.org/viewvc/llvm-project?rev=246266&view=rev Log: [libcxx] Optimize away unneeded length calculation in basic_string::compare(const char*)
Summary: This patch optimizes basic_string::compare to use strcmp when the default char_traits has been given. See PR19900 for more information. https://llvm.org/bugs/show_bug.cgi?id=19900 Reviewers: mclow.lists Subscribers: bkramer, cfe-commits Differential Revision: http://reviews.llvm.org/D12355 Modified: libcxx/trunk/include/string Modified: libcxx/trunk/include/string URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/string?rev=246266&r1=246265&r2=246266&view=diff ============================================================================== --- libcxx/trunk/include/string (original) +++ libcxx/trunk/include/string Thu Aug 27 22:02:37 2015 @@ -3795,7 +3795,11 @@ bool operator==(const _CharT* __lhs, const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT { - return __rhs.compare(__lhs) == 0; + typedef basic_string<_CharT, _Traits, _Allocator> _String; + _LIBCPP_ASSERT(__lhs != nullptr, "operator==(char*, basic_string): received nullptr"); + size_t __lhs_len = _Traits::length(__lhs); + if (__lhs_len != __rhs.size()) return false; + return __rhs.compare(0, _String::npos, __lhs, __lhs_len) == 0; } template<class _CharT, class _Traits, class _Allocator> @@ -3804,7 +3808,11 @@ bool operator==(const basic_string<_CharT,_Traits,_Allocator>& __lhs, const _CharT* __rhs) _NOEXCEPT { - return __lhs.compare(__rhs) == 0; + typedef basic_string<_CharT, _Traits, _Allocator> _String; + _LIBCPP_ASSERT(__rhs != nullptr, "operator==(basic_string, char*): received nullptr"); + size_t __rhs_len = _Traits::length(__rhs); + if (__rhs_len != __lhs.size()) return false; + return __lhs.compare(0, _String::npos, __rhs, __rhs_len) == 0; } // operator!= _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
