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re PR libstdc++/4150 (catastrophic performance decrease in C++ code)

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PR libstdc++/4150
        * include/std/std_streambuf.h (basic_streambuf::_M_set_indeterminate):
        Move to filebuf.
        (basic_streambuf::_M_set_determinate): Likewise.
        (basic_streambuf::_M_is_indeterminate): Likewise.
        * include/bits/std_fstream.h (basic_filebuf::_M_filepos): New
        non-static data member.
        (basic_filebuf::_M_underflow_common): New non-static member function.
        (basic_filebuf::_M_underflow, _M_uflow): Call it.
        (basic_filebuf::sync): Avoid useless seeking.
        (basic_filebuf::_M_set_indeterminate): Move here from streambuf.
        Set _M_filepos.
        (basic_filebuf::_M_set_determinate): Likewise.
        (basic_filebuf::_M_is_indeterminate): Likewise.
        * include/bits/fstream.tcc (basic_filebuf::_M_really_overflow): Seek
        back to _M_out_beg if necessary.
        (basic_filebuf::seekoff): Likewise.
        (basic_filebuf::_M_underflow_common): Generalization of old
        underflow().  Don't seek back to _M_in_beg.
        * src/ios.cc: Lose _GLIBCPP_AVOID_FSEEK stuff.
        * config/os/solaris/solaris2.?/bits/os_defines.h: Likewise.
        * config/os/bsd/freebsd/bits/os_defines.h: Likewise.
        * config/os/mingw32/bits/os_defines.h: Likewise.
        * testsuite/27_io/filebuf_virtuals.cc (test05): Don't overspecify
        ungetc test.

From-SVN: r52634
This commit is contained in:
Jason Merrill 2002-04-22 16:28:05 -04:00 committed by Jason Merrill
parent f942d7a5df
commit 5066927d9e
11 changed files with 118 additions and 86 deletions
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28
libstdc++-v3/ChangeLog
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@ -1,3 +1,31 @@
2002-04-20 Jason Merrill <jason@redhat.com>
PR libstdc++/4150
* include/std/std_streambuf.h (basic_streambuf::_M_set_indeterminate):
Move to filebuf.
(basic_streambuf::_M_set_determinate): Likewise.
(basic_streambuf::_M_is_indeterminate): Likewise.
* include/bits/std_fstream.h (basic_filebuf::_M_filepos): New
non-static data member.
(basic_filebuf::_M_underflow_common): New non-static member function.
(basic_filebuf::_M_underflow, _M_uflow): Call it.
(basic_filebuf::sync): Avoid useless seeking.
(basic_filebuf::_M_set_indeterminate): Move here from streambuf.
Set _M_filepos.
(basic_filebuf::_M_set_determinate): Likewise.
(basic_filebuf::_M_is_indeterminate): Likewise.
* include/bits/fstream.tcc (basic_filebuf::_M_really_overflow): Seek
back to _M_out_beg if necessary.
(basic_filebuf::seekoff): Likewise.
(basic_filebuf::_M_underflow_common): Generalization of old
underflow(). Don't seek back to _M_in_beg.
* src/ios.cc: Lose _GLIBCPP_AVOID_FSEEK stuff.
* config/os/solaris/solaris2.?/bits/os_defines.h: Likewise.
* config/os/bsd/freebsd/bits/os_defines.h: Likewise.
* config/os/mingw32/bits/os_defines.h: Likewise.
* testsuite/27_io/filebuf_virtuals.cc (test05): Don't overspecify
ungetc test.
2002-04-22 Benjamin Kosnik <bkoz@redhat.com>
* include/bits/istream.tcc (istream::read): Fix.

2
libstdc++-v3/config/os/bsd/freebsd/bits/os_defines.h
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@ -36,6 +36,4 @@
#define __glibcpp_long_double_bits __glibcpp_double_bits
#define _GLIBCPP_AVOID_FSEEK 1
#endif

3
libstdc++-v3/config/os/mingw32/bits/os_defines.h
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@ -34,7 +34,4 @@
// System-specific #define, typedefs, corrections, etc, go here. This
// file will come before all others.
#define _GLIBCPP_AVOID_FSEEK 1
#endif

2
libstdc++-v3/config/os/solaris/solaris2.5/bits/os_defines.h
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@ -33,8 +33,6 @@
// System-specific #define, typedefs, corrections, etc, go here. This
// file will come before all others.
#define _GLIBCPP_AVOID_FSEEK 1
// These are typedefs which libio assumes are already in place (because
// they really are, under Linux).
#define __off_t off_t

2
libstdc++-v3/config/os/solaris/solaris2.6/bits/os_defines.h
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@ -33,8 +33,6 @@
// System-specific #define, typedefs, corrections, etc, go here. This
// file will come before all others.
#define _GLIBCPP_AVOID_FSEEK 1
// These are typedefs which libio assumes are already in place (because
// they really are, under Linux).
#define __off_t off_t

2
libstdc++-v3/config/os/solaris/solaris2.7/bits/os_defines.h
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@ -33,8 +33,6 @@
// System-specific #define, typedefs, corrections, etc, go here. This
// file will come before all others.
#define _GLIBCPP_AVOID_FSEEK 1
// These are typedefs which libio assumes are already in place (because
// they really are, under Linux).
#define __off_t off_t

38
libstdc++-v3/include/bits/fstream.tcc
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@ -206,7 +206,7 @@ namespace std
template<typename _CharT, typename _Traits>
typename basic_filebuf<_CharT, _Traits>::int_type
basic_filebuf<_CharT, _Traits>::
underflow()
_M_underflow_common(bool __bump)
{
int_type __ret = traits_type::eof();
bool __testin = _M_mode & ios_base::in;
@ -232,12 +232,8 @@ namespace std
{
if (__testout)
_M_really_overflow();
#if _GLIBCPP_AVOID_FSEEK
else if ((_M_in_cur - _M_in_beg) == 1)
_M_file.sys_getc();
#endif
else
_M_file.seekoff(_M_in_cur - _M_in_beg,
else if (_M_in_cur != _M_filepos)
_M_file.seekoff(_M_in_cur - _M_filepos,
ios_base::cur, ios_base::in);
}
@ -280,16 +276,16 @@ namespace std
if (__testout)
_M_out_cur = _M_in_cur;
__ret = traits_type::to_int_type(*_M_in_cur);
#if _GLIBCPP_AVOID_FSEEK
if (__elen == 1)
_M_file.sys_ungetc(*_M_in_cur);
else
if (__bump)
_M_in_cur_move(1);
else if (_M_buf_size == 1)
{
#endif
_M_file.seekoff(-__elen, ios_base::cur, ios_base::in);
#if _GLIBCPP_AVOID_FSEEK
// If we are synced with stdio, we have to unget the
// character we just read so that the file pointer
// doesn't move.
_M_file.sys_ungetc(*_M_in_cur);
_M_set_indeterminate();
}
#endif
}
}
}
@ -464,6 +460,15 @@ namespace std
streamsize __elen = 0;
streamsize __plen = 0;
// Need to restore current position. The position of the external
// byte sequence (_M_file) corresponds to _M_filepos, and we need
// to move it to _M_out_beg for the write.
if (_M_filepos && _M_filepos != _M_out_beg)
{
off_type __off = _M_out_beg - _M_filepos;
_M_file.seekoff(__off, ios_base::cur);
}
// Convert internal buffer to external representation, output.
// NB: In the unbuffered case, no internal buffer exists.
if (!__testunbuffered)
@ -551,9 +556,8 @@ namespace std
_M_output_unshift();
}
//in
// NB: underflow() rewinds the external buffer.
else if (__testget && __way == ios_base::cur)
__computed_off += _M_in_cur - _M_in_beg;
__computed_off += _M_in_cur - _M_filepos;
__ret = _M_file.seekoff(__computed_off, __way, __mode);
_M_set_indeterminate();

74
libstdc++-v3/include/std/std_fstream.h
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@ -93,6 +93,10 @@ namespace std
// XXX Needed?
bool _M_last_overflowed;
// The position in the buffer corresponding to the external file
// pointer.
char_type* _M_filepos;
public:
// Constructors/destructor:
basic_filebuf();
@ -137,8 +141,21 @@ namespace std
// underflow() and uflow() functions are called to get the next
// charater from the real input source when the buffer is empty.
// Buffered input uses underflow()
// The only difference between underflow() and uflow() is that the
// latter bumps _M_in_cur after the read. In the sync_with_stdio
// case, this is important, as we need to unget the read character in
// the underflow() case in order to maintain synchronization. So
// instead of calling underflow() from uflow(), we create a common
// subroutine to do the real work.
int_type
_M_underflow_common(bool __bump);
virtual int_type
underflow();
underflow() { return _M_underflow_common(false); }
virtual int_type
uflow() { return _M_underflow_common(true); }
virtual int_type
pbackfail(int_type __c = _Traits::eof());
@ -189,14 +206,11 @@ namespace std
// the file position with the external file.
if (__testput && !_M_file.sync())
{
// Need to restore current position. This interpreted as
// the position of the external byte sequence (_M_file)
// plus the offset in the current internal buffer
// (_M_out_beg - _M_out_cur)
streamoff __cur = _M_file.seekoff(0, ios_base::cur);
off_type __off = _M_out_cur - _M_out_beg;
// Need to restore current position after the write.
off_type __off = _M_out_cur - _M_out_end;
_M_really_overflow();
_M_file.seekpos(__cur + __off);
if (__off)
_M_file.seekoff(__off, ios_base::cur);
}
_M_last_overflowed = false;
return 0;
@ -235,6 +249,50 @@ namespace std
void
_M_output_unshift();
// These three functions are used to clarify internal buffer
// maintenance. After an overflow, or after a seekoff call that
// started at beg or end, or possibly when the stream becomes
// unbuffered, and a myrid other obscure corner cases, the
// internal buffer does not truly reflect the contents of the
// external buffer. At this point, for whatever reason, it is in
// an indeterminate state.
void
_M_set_indeterminate(void)
{
if (_M_mode & ios_base::in)
this->setg(_M_buf, _M_buf, _M_buf);
if (_M_mode & ios_base::out)
this->setp(_M_buf, _M_buf);
_M_filepos = _M_in_end;
}
void
_M_set_determinate(off_type __off)
{
bool __testin = _M_mode & ios_base::in;
bool __testout = _M_mode & ios_base::out;
if (__testin)
this->setg(_M_buf, _M_buf, _M_buf + __off);
if (__testout)
this->setp(_M_buf, _M_buf + __off);
_M_filepos = _M_in_end;
}
bool
_M_is_indeterminate(void)
{
bool __ret = false;
// Don't return true if unbuffered.
if (_M_buf)
{
if (_M_mode & ios_base::in)
__ret = _M_in_beg == _M_in_cur && _M_in_cur == _M_in_end;
if (_M_mode & ios_base::out)
__ret = _M_out_beg == _M_out_cur && _M_out_cur == _M_out_end;
}
return __ret;
}
};

42
libstdc++-v3/include/std/std_streambuf.h
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@ -231,48 +231,6 @@ namespace std
return __ret;
}
// These three functions are used to clarify internal buffer
// maintenance. After an overflow, or after a seekoff call that
// started at beg or end, or possibly when the stream becomes
// unbuffered, and a myrid other obscure corner cases, the
// internal buffer does not truly reflect the contents of the
// external buffer. At this point, for whatever reason, it is in
// an indeterminate state.
void
_M_set_indeterminate(void)
{
if (_M_mode & ios_base::in)
this->setg(_M_buf, _M_buf, _M_buf);
if (_M_mode & ios_base::out)
this->setp(_M_buf, _M_buf);
}
void
_M_set_determinate(off_type __off)
{
bool __testin = _M_mode & ios_base::in;
bool __testout = _M_mode & ios_base::out;
if (__testin)
this->setg(_M_buf, _M_buf, _M_buf + __off);
if (__testout)
this->setp(_M_buf, _M_buf + __off);
}
bool
_M_is_indeterminate(void)
{
bool __ret = false;
// Don't return true if unbuffered.
if (_M_buf)
{
if (_M_mode & ios_base::in)
__ret = _M_in_beg == _M_in_cur && _M_in_cur == _M_in_end;
if (_M_mode & ios_base::out)
__ret = _M_out_beg == _M_out_cur && _M_out_cur == _M_out_end;
}
return __ret;
}
public:
virtual
~basic_streambuf()

8
libstdc++-v3/src/ios.cc
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@ -150,14 +150,6 @@ namespace std
int __out_bufsize = __sync ? 0 : static_cast<int>(BUFSIZ);
int __in_bufsize = __sync ? 1 : static_cast<int>(BUFSIZ);
#if _GLIBCPP_AVOID_FSEEK
// Platforms that prefer to avoid fseek() calls on streams only
// get their desire when the C++-layer input buffer size is 1.
// This hack hurts performance but keeps correctness across
// all types of streams that might be attached to (e.g.) cin.
__in_bufsize = 1;
#endif
// NB: The file globals.cc creates the four standard files
// with NULL buffers. At this point, we swap out the dummy NULL
// [io]stream objects and buffers with the real deal.

3
libstdc++-v3/testsuite/27_io/filebuf_virtuals.cc
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@ -444,6 +444,9 @@ void test05()
strmsz_1 = fb_03.sputn("because because because. . .", 28);
VERIFY( strmsz_1 == 28 );
c1 = fb_03.sungetc();
// Defect? retval of sungetc is not necessarily the character ungotten.
// So re-get it.
c1 = fb_03.sgetc();
fb_03.pubsync();
c3 = fb_03.sgetc();
VERIFY( c1 == c3 );