why does arm-target gcc-3.4.4 have a better performace than gcc-4.2.4?

Ian Lance Taylor iant@google.com
Wed Jun 23 00:06:00 GMT 2010

Heyu Zhu <zhu.heyu@gmail.com> writes:

> I configure gcc as below
> ../gcc-4.2.4(or gcc-3.4.4)/configure
>                --target=arm-elf
>                --prefix=/usr/local/arm
>                --enable-languages=c
>                --without-headers
>                --with-gnu-ld
>                --with-gnu-as
>                --disable-shared
>                --disable-threads
>                --disable-libssp
>  Executable binary file generated by gcc-3.4.4 is 15% faster than by
> gcc-4.2.4 for some test programs, for example, Dhrystone.
> Need i configure gcc-4.2.4 with special options to get a good
> performace as gcc-3.4.4 does?

There are no configure options which will make a difference here.
There may be some runtime options which will help.  In particular,
make sure you use -O2 and use a -march option appropriate for your

It is of course entirely possible that there has been some
optimization regression in gcc.  If you can pin down the code which is
slower, please open a bug report with a test case as described at
http://gcc.gnu.org/bugs/ .  Thanks.


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