From 1e1a3ecee9423b3450cd76b92b376ee39a8924ac Mon Sep 17 00:00:00 2001
From: paolo <paolo@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Sun, 19 Dec 2010 15:53:44 +0000
Subject: 2010-12-19  Paolo Carlini  <paolo.carlini@oracle.com>

	* include/bits/basic_string.h (operator+(basic_string<>&&,
	basic_string<>&&)): Optimize better.
	* include/ext/vstring.h (operator+(__versa_string<>&&,
	__versa_string<>&)): Likewise.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@168061 138bc75d-0d04-0410-961f-82ee72b054a4
---
 libstdc++-v3/ChangeLog                   |  7 +++++++
 libstdc++-v3/include/bits/basic_string.h | 12 +++++++++---
 libstdc++-v3/include/ext/vstring.h       |  8 +++++++-
 3 files changed, 23 insertions(+), 4 deletions(-)

(limited to 'libstdc++-v3')

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 19063dd7b22..b6f23e4413b 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,10 @@
+2010-12-19  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	* include/bits/basic_string.h (operator+(basic_string<>&&,
+	basic_string<>&&)): Optimize better.
+	* include/ext/vstring.h (operator+(__versa_string<>&&,
+	__versa_string<>&)): Likewise.
+
 2010-12-19  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* testsuite/21_strings/basic_string/operators/char/4.cc: New.
diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index eb27e677e12..bffa8afd4c6 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -2380,7 +2380,13 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
     inline basic_string<_CharT, _Traits, _Alloc>
     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
 	      basic_string<_CharT, _Traits, _Alloc>&& __rhs)
-    { return std::move(__lhs.append(__rhs)); }
+    {
+      const auto __size = __lhs.size() + __rhs.size();
+      const bool __cond = (__size > __lhs.capacity()
+			   && __size <= __rhs.capacity());
+      return __cond ? std::move(__rhs.insert(0, __lhs))
+	            : std::move(__lhs.append(__rhs));
+    }
 
   template<typename _CharT, typename _Traits, typename _Alloc>
     inline basic_string<_CharT, _Traits, _Alloc>
@@ -2390,8 +2396,8 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
 
   template<typename _CharT, typename _Traits, typename _Alloc>
     inline basic_string<_CharT, _Traits, _Alloc>
-    operator+(_CharT __lhs, basic_string<_CharT,
-	      _Traits, _Alloc>&& __rhs)
+    operator+(_CharT __lhs,
+	      basic_string<_CharT, _Traits, _Alloc>&& __rhs)
     { return std::move(__rhs.insert(0, 1, __lhs)); }
 
   template<typename _CharT, typename _Traits, typename _Alloc>
diff --git a/libstdc++-v3/include/ext/vstring.h b/libstdc++-v3/include/ext/vstring.h
index faca91be509..3700f3ee587 100644
--- a/libstdc++-v3/include/ext/vstring.h
+++ b/libstdc++-v3/include/ext/vstring.h
@@ -2118,7 +2118,13 @@ _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
     inline __versa_string<_CharT, _Traits, _Alloc, _Base>
     operator+(__versa_string<_CharT, _Traits, _Alloc, _Base>&& __lhs,
 	      __versa_string<_CharT, _Traits, _Alloc, _Base>&& __rhs)
-    { return std::move(__lhs.append(__rhs)); }
+    {
+      const auto __size = __lhs.size() + __rhs.size();
+      const bool __cond = (__size > __lhs.capacity()
+			   && __size <= __rhs.capacity());
+      return __cond ? std::move(__rhs.insert(0, __lhs))
+	            : std::move(__lhs.append(__rhs));
+    }
 
   template<typename _CharT, typename _Traits, typename _Alloc,
 	   template <typename, typename, typename> class _Base>
-- 
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