[Bug c/38518] New: Excessive compile time with -O3

[Bug c/38518] New: Excessive compile time with -O3

[dcb314 at hotmail dot com]

I just tried to compile the package fceu-0.98.25-1.7
with the GNU C++ compiler version 4.4 snapshot 20081212.

The compiler appears to get into a long or possibly infinite loop.
I tried compiling with flag -O2 and that took 40 seconds or so.
With flag -O3, compilation did not finish in over seven minutes on
an otherwise idle machine.

Preprocessed source code attached. Flag -O3 required.


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           Summary: Excessive compile time with -O3
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dcb314 at hotmail dot com
  GCC host triplet: suse-linux-x86_64


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38518

[Bug c/38518] Excessive compile time with -O3

[dcb314 at hotmail dot com]

------- Comment #1 from dcb314 at hotmail dot com  2008-12-13 18:18 -------
Created an attachment (id=16904)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16904&action=view)
C source code


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38518

[Bug c/38518] Excessive compile time with -O3

[hjl dot tools at gmail dot com]

------- Comment #2 from hjl dot tools at gmail dot com  2008-12-13 19:50 -------
On 2.66GHz Cor2 Quad running Fedora 9/x86-64, gcc 4.4 revision 142740 gave:

lake:pts/1[9]> time ./xgcc -B./ -O3 /tmp/bug48.c -S
./xgcc -B./ -O3 /tmp/bug48.c -S  94.39s user 0.98s system 99% cpu 1:35.51 total
lake:pts/1[10]> time ./xgcc -B./ -O2 /tmp/bug48.c -S        
./xgcc -B./ -O2 /tmp/bug48.c -S  11.66s user 0.22s system 99% cpu 11.877 total
lake:pts/1[11]> time ./xgcc -B./ -O2 /tmp/bug48.c -S -ftree-vectorize
./xgcc -B./ -O2 /tmp/bug48.c -S -ftree-vectorize  61.16s user 0.73s system 99%
cpu 1:01.92 total


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hjl dot tools at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hjl dot tools at gmail dot
                   |                            |com
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |WORKSFORME


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38518

[Bug c/38518] Excessive compile time with -O3

[dcb314 at hotmail dot com]

------- Comment #3 from dcb314 at hotmail dot com  2008-12-14 09:52 -------
(In reply to comment #2)
> On 2.66GHz Cor2 Quad running Fedora 9/x86-64, gcc 4.4 revision 142740 gave:

Thanks for the extra information.

I am concerned that the -O3 takes nine times longer than the -O2.

I'd be interested in finding out where that extra time is 
being spent. I've had a look at "man gcc" but nothing obvious 
is found.


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dcb314 at hotmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|WORKSFORME                  |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38518