[v3] Fix libstdc++/16401

[Paolo Carlini <pcarlini at suse dot de>]

Hi,

the below fixes a serious performance regression in 3.4/mainline: when
I tweaked Nathan's rewrite of stringbuf::overflow to spare a copy, I
forgot, my bad, that now __tmp was a *new* string and I couldn't rely
on it growing automatically exponentially from the old _M_string size.

Tested x86-linux.

Paolo.

//////////////
2004-07-07  Paolo Carlini  <pcarlini@suse.de>

	PR libstdc++/16401
	* include/bits/sstream.tcc (overflow): When reallocating _M_string
	use an exponential grow policy.
	* testsuite/27_io/basic_stringbuf/overflow/char/1.cc: New.
	* testsuite/performance/27_io/stringbuf_overflow.cc: New.

diff -prN libstdc++-v3-orig/include/bits/sstream.tcc libstdc++-v3/include/bits/sstream.tcc
*** libstdc++-v3-orig/include/bits/sstream.tcc	Sun Feb  8 05:46:41 2004
--- libstdc++-v3/include/bits/sstream.tcc	Wed Jul  7 13:07:50 2004
*************** namespace std
*** 83,105 ****
        if (__builtin_expect(__testeof, false))
  	return traits_type::not_eof(__c);
  
!       // NB: Start ostringstream buffers at 512 chars. This is an
!       // experimental value (pronounced "arbitrary" in some of the
!       // hipper english-speaking countries), and can be changed to
!       // suit particular needs.
!       const __size_type __len = std::max(__size_type(_M_string.capacity() + 1),
! 					 __size_type(512));
        const bool __testput = this->pptr() < this->epptr();
!       if (__builtin_expect(!__testput && __len > _M_string.max_size(), false))
  	return traits_type::eof();
  
        // Try to append __c into output sequence in one of two ways.
        // Order these tests done in is unspecified by the standard.
        if (!__testput)
  	{
! 	  // In virtue of DR 169 (TC) we are allowed to grow more than
! 	  // one char. That's easy to implement thanks to the exponential
! 	  // growth policy builtin into basic_string.
  	  __string_type __tmp;
  	  __tmp.reserve(__len);
  	  __tmp.assign(_M_string.data(), this->epptr() - this->pbase());
--- 83,107 ----
        if (__builtin_expect(__testeof, false))
  	return traits_type::not_eof(__c);
  
!       const __size_type __capacity = _M_string.capacity();
!       const __size_type __max_size = _M_string.max_size();
        const bool __testput = this->pptr() < this->epptr();
!       if (__builtin_expect(!__testput && __capacity == __max_size, false))
  	return traits_type::eof();
  
        // Try to append __c into output sequence in one of two ways.
        // Order these tests done in is unspecified by the standard.
        if (!__testput)
  	{
! 	  // NB: Start ostringstream buffers at 512 chars. This is an
! 	  // experimental value (pronounced "arbitrary" in some of the
! 	  // hipper english-speaking countries), and can be changed to
! 	  // suit particular needs.
! 	  // Then, in virtue of DR 169 (TC) we are allowed to grow more
! 	  // than one char.
! 	  const __size_type __opt_len = std::max(__size_type(2 * __capacity),
! 						 __size_type(512));
! 	  const __size_type __len = std::min(__opt_len, __max_size);
  	  __string_type __tmp;
  	  __tmp.reserve(__len);
  	  __tmp.assign(_M_string.data(), this->epptr() - this->pbase());
diff -prN libstdc++-v3-orig/testsuite/27_io/basic_stringbuf/overflow/char/1.cc libstdc++-v3/testsuite/27_io/basic_stringbuf/overflow/char/1.cc
*** libstdc++-v3-orig/testsuite/27_io/basic_stringbuf/overflow/char/1.cc	Thu Jan  1 01:00:00 1970
--- libstdc++-v3/testsuite/27_io/basic_stringbuf/overflow/char/1.cc	Wed Jul  7 13:31:03 2004
***************
*** 0 ****
--- 1,57 ----
+ // 2004-07-07  Paolo Carlini  <pcarlini@suse.de>
+ 
+ // Copyright (C) 2004 Free Software Foundation, Inc.
+ //
+ // This file is part of the GNU ISO C++ Library.  This library is free
+ // software; you can redistribute it and/or modify it under the
+ // terms of the GNU General Public License as published by the
+ // Free Software Foundation; either version 2, or (at your option)
+ // any later version.
+ 
+ // This library is distributed in the hope that it will be useful,
+ // but WITHOUT ANY WARRANTY; without even the implied warranty of
+ // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ // GNU General Public License for more details.
+ 
+ // You should have received a copy of the GNU General Public License along
+ // with this library; see the file COPYING.  If not, write to the Free
+ // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+ // USA.
+ 
+ // 27.7.1.3 basic_stringbuf overridden virtual functions.
+ 
+ #include <sstream>
+ #include <cstdlib>
+ #include <testsuite_hooks.h>
+ 
+ using namespace std;
+ 
+ string
+ data(long len)
+ {
+   string ret;
+   for (long i = 0; i < len; ++i)
+     ret.push_back('a' + rand() % 26);
+   return ret;
+ }
+ 
+ void
+ test01(int iter)
+ {
+   bool test __attribute__((unused)) = true;
+ 
+   for (unsigned n = 1; n <= iter; n *= 10)
+     {
+       const string str = data(n);
+       stringbuf sstr;
+       for (unsigned i = 0; i < n; ++i)
+ 	sstr.sputc(str[i]);
+       VERIFY( str == sstr.str() );
+     }
+ }
+ 
+ int main()
+ {
+   test01(10000000);
+   return 0;
+ }
diff -prN libstdc++-v3-orig/testsuite/performance/27_io/stringbuf_overflow.cc libstdc++-v3/testsuite/performance/27_io/stringbuf_overflow.cc
*** libstdc++-v3-orig/testsuite/performance/27_io/stringbuf_overflow.cc	Thu Jan  1 01:00:00 1970
--- libstdc++-v3/testsuite/performance/27_io/stringbuf_overflow.cc	Wed Jul  7 13:05:10 2004
***************
*** 0 ****
--- 1,60 ----
+ // Copyright (C) 2004 Free Software Foundation, Inc.
+ //
+ // This file is part of the GNU ISO C++ Library.  This library is free
+ // software; you can redistribute it and/or modify it under the
+ // terms of the GNU General Public License as published by the
+ // Free Software Foundation; either version 2, or (at your option)
+ // any later version.
+ 
+ // This library is distributed in the hope that it will be useful,
+ // but WITHOUT ANY WARRANTY; without even the implied warranty of
+ // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ // GNU General Public License for more details.
+ 
+ // You should have received a copy of the GNU General Public License along
+ // with this library; see the file COPYING.  If not, write to the Free
+ // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+ // USA.
+ 
+ // As a special exception, you may use this file as part of a free software
+ // library without restriction.  Specifically, if other files instantiate
+ // templates or use macros or inline functions from this file, or you compile
+ // this file and link it with other files to produce an executable, this
+ // file does not by itself cause the resulting executable to be covered by
+ // the GNU General Public License.  This exception does not however
+ // invalidate any other reasons why the executable file might be covered by
+ // the GNU General Public License.
+ 
+ #include <sstream>
+ #include <testsuite_performance.h>
+ 
+ // libstdc++/16401 ostringstream in gcc 3.4.x very slow for big data
+ void test01()
+ {
+   using namespace std;
+   using namespace __gnu_test;
+ 
+   time_counter time;
+   resource_counter resource;
+ 
+   for(unsigned n = 10000; n <= 10000000; n *= 10)
+     {
+       ostringstream oss;
+       oss << "size = " << n; 
+ 
+       ostringstream str;
+       start_counters(time, resource);  
+       for(unsigned i = 0; i < n; ++i)
+ 	str << 'a';
+       stop_counters(time, resource);
+ 
+       report_performance(__FILE__, oss.str(), time, resource);
+       clear_counters(time, resource);
+     }
+ }
+ 
+ int main()
+ {
+   test01();
+   return 0;
+ }