From 08dd25303ed29c94787e46f4f766078a36c366ed Mon Sep 17 00:00:00 2001
From: Howard Hinnant <hhinnant@apple.com>
Date: Mon, 22 Apr 2013 23:55:13 +0000
Subject: [PATCH] Modest performance improvement for std::string's operator==.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@180072 91177308-0d34-0410-b5e6-96231b3b80d8
---
include/string | 35 ++++++++++++++++++++++++++++-------
1 file changed, 28 insertions(+), 7 deletions(-)
diff --git a/include/string b/include/string
index de668bba..fa44f68e 100644
--- a/include/string
+++ b/include/string
@@ -1462,6 +1462,11 @@ public:
int compare(size_type __pos1, size_type __n1, const_pointer __s, size_type __n2) const;
_LIBCPP_INLINE_VISIBILITY bool __invariants() const;
+
+ _LIBCPP_INLINE_VISIBILITY
+ bool __is_long() const _NOEXCEPT
+ {return bool(__r_.first().__s.__size_ & __short_mask);}
+
private:
_LIBCPP_INLINE_VISIBILITY
allocator_type& __alloc() _NOEXCEPT
@@ -1470,10 +1475,6 @@ private:
const allocator_type& __alloc() const _NOEXCEPT
{return __r_.second();}
- _LIBCPP_INLINE_VISIBILITY
- bool __is_long() const _NOEXCEPT
- {return bool(__r_.first().__s.__size_ & __short_mask);}
-
_LIBCPP_INLINE_VISIBILITY
void __set_short_size(size_type __s) _NOEXCEPT
#if _LIBCPP_BIG_ENDIAN
@@ -3561,9 +3562,29 @@ bool
operator==(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
{
- return __lhs.size() == __rhs.size() && _Traits::compare(__lhs.data(),
- __rhs.data(),
- __lhs.size()) == 0;
+ size_t __lhs_sz = __lhs.size();
+ return __lhs_sz == __rhs.size() && _Traits::compare(__lhs.data(),
+ __rhs.data(),
+ __lhs_sz) == 0;
+}
+
+template<class _Allocator>
+_LIBCPP_INLINE_VISIBILITY inline
+bool
+operator==(const basic_string<char, char_traits<char>, _Allocator>& __lhs,
+ const basic_string<char, char_traits<char>, _Allocator>& __rhs) _NOEXCEPT
+{
+ size_t __lhs_sz = __lhs.size();
+ if (__lhs_sz != __rhs.size())
+ return false;
+ const char* __lp = __lhs.data();
+ const char* __rp = __rhs.data();
+ if (__lhs.__is_long())
+ return char_traits<char>::compare(__lp, __rp, __lhs_sz) == 0;
+ for (; __lhs_sz != 0; --__lhs_sz, ++__lp, ++__rp)
+ if (*__lp != *__rp)
+ return false;
+ return true;
}
template<class _CharT, class _Traits, class _Allocator>