[Bug c++/24208] New: C++ front-end can still be sped up

[Bug c++/24208] New: C++ front-end can still be sped up

[sabre at nondot dot org]

Here's a case where the C++ front-end is still slow, despite the great
improvements in GCC 4.  This is preprocessed with Apple's 4.x compiler.

From, 'g++ IC.ii -ftime-report -O0 -o /dev/null -S', I get:

 parser                :   1.84 (27%) usr   1.48 (29%) sys   3.22 (27%) wall
 name lookup           :   1.47 (22%) usr   2.59 (51%) sys   4.06 (34%) wall
...
 TOTAL                 :   6.73             5.04            11.88

On a somewhat scary note, compiling without -ftime-report speeds up the
compilation from 0:11.95 to 0:04.39.  This leads me to believe that the
-ftime-report numbers can't be trusted very much.

More testcases are always good right?

-Chris


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           Summary: C++ front-end can still be sped up
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sabre at nondot dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24208

[Bug c++/24208] C++ front-end can still be sped up

[sabre at nondot dot org]

------- Comment #1 from sabre at nondot dot org  2005-10-05 00:03 -------
Created an attachment (id=9886)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=9886&action=view)
Large C++ file


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24208

[Bug c++/24208] C++ front-end can still be sped up

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2005-10-05 00:08 -------
(In reply to comment #0)
> On a somewhat scary note, compiling without -ftime-report speeds up the
> compilation from 0:11.95 to 0:04.39.  This leads me to believe that the
> -ftime-report numbers can't be trusted very much.

This is because Darwin's timing functions are slow.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |compile-time-hog
            Version|unknown                     |4.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24208

[Bug c++/24208] C++ front-end can still be sped up

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2005-10-09 18:39 -------
Confirmed.  The middle-end problems are almost all in reload.c.

For the profile, everything is just spread all around.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24208

[Bug c++/24208] C++ front-end can still be sped up

[pinskia at gcc dot gnu dot org]

------- Comment #4 from pinskia at gcc dot gnu dot org  2005-10-09 18:48 -------
I think this is just a problem of templates, lots of them.


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pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-10-09 18:48:55
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24208

[Bug c++/24208] C++ front-end can still be sped up

[sabre at nondot dot org]

------- Comment #5 from sabre at nondot dot org  2005-10-09 22:02 -------
Some updates: the -ftime-report problems were a local problem with apple's gcc,
now fixed.  This testcase has some templates (e.g. the match stuff), but mostly
it is just big branchy compiler code :), not atypical of many C++ programs.

-Chris


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24208

[Bug c++/24208] C++ front-end can still be sped up

[pinskia at gcc dot gnu dot org]

------- Comment #6 from pinskia at gcc dot gnu dot org  2006-11-15 04:46 -------
In 4.2.0 on i686-linux-gnu this is much better:
 parser                :   1.99 (31%) usr   0.28 (28%) sys   2.42 (25%) wall  
43674 kB (49%) ggc
 name lookup           :   0.48 ( 7%) usr   0.37 (37%) sys   1.51 (16%) wall   
5041 kB ( 6%) ggc


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24208

[Bug c++/24208] C++ front-end can still be sped up

[pinskia at gcc dot gnu dot org]

------- Comment #7 from pinskia at gcc dot gnu dot org  2006-11-15 04:48 -------
Note, I am not going to close this bug just yet because this testcase produces
some weird -O2 timing results for 4.2.0:
 tree operand scan     :  11.29 (27%) usr   0.51 (22%) sys  13.09 (25%) wall   
9015 kB ( 4%) ggc


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24208

[Bug c++/24208] C++ front-end can still be sped up

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24208

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
The testcase no longer works, even after unincluding.  There have been
improvements to the operand scanner, so let's close it as fixed.