[Bug target/21314] C++ performance regression with -Os

["deemkay at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From deemkay at gmail dot com  2005-05-02 01:17 -------
dirtyepic ~/work $ ~/gcc-4.0-20050430/bin/g++ -O0 -Wall -march=pentium3
cpptest.cpp -o new-pr21314-O0
dirtyepic ~/work $ ~/gcc-4.0-20050430/bin/g++ -O1 -Wall -march=pentium3
cpptest.cpp -o new-pr21314-O1
dirtyepic ~/work $ ~/gcc-4.0-20050430/bin/g++ -O2 -Wall -march=pentium3
cpptest.cpp -o new-pr21314-O2
dirtyepic ~/work $ ~/gcc-4.0-20050430/bin/g++ -O3 -Wall -march=pentium3
cpptest.cpp -o new-pr21314-O3
dirtyepic ~/work $ ~/gcc-4.0-20050430/bin/g++ -Os -Wall -march=pentium3
cpptest.cpp -o new-pr21314-Os

-rwxr-xr-x  1 dirtyepic users  15609 May  1 18:59 new-pr21314-O0
-rwxr-xr-x  1 dirtyepic users   8245 May  1 18:59 new-pr21314-O1
-rwxr-xr-x  1 dirtyepic users   8317 May  1 18:59 new-pr21314-O2
-rwxr-xr-x  1 dirtyepic users   8069 May  1 18:59 new-pr21314-O3
-rwxr-xr-x  1 dirtyepic users  12901 May  1 18:59 new-pr21314-Os

dirtyepic ~/work $ ./new-pr21314-O0
0
time: 20.420000
dirtyepic ~/work $ ./new-pr21314-O1
0
time: 7.490000
dirtyepic ~/work $ ./new-pr21314-O2
0
time: 6.950000
dirtyepic ~/work $ ./new-pr21314-O3
0
time: 7.030000
dirtyepic ~/work $ ./new-pr21314-Os
0
time: 16.680000

the performance regression i can understand is not a priority.  but the size
regression is surprising.

dirtyepic ~/work $ ~/gcc-4.0-20050430/bin/g++ -v                               
                    Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../gcc-4.0-20050430/configure
--enable-version-specific-runtime-libs
--prefix=/home/dirtyepic/gcc-4.0-20050430/ --host=i686-pc-linux-gnu
--build=i686-pc-linux-gnu --disable-altivec --disable-nls --with-system-zlib
--disable-checking --disable-werror --disable-libunwind-exceptions
--disable-multilib --disable-libgcj --enable-languages=c,c++ --enable-shared
--enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
Thread model: posix
gcc version 4.0.1 20050430 (prerelease)

let me know if there's any other data that would help.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21314