[Bug target/25500] REGREGRESSION: SSE2 vectorized code is many times slower on 4.x.x than on 3.4.4

["yuri at tsoft dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #11 from yuri at tsoft dot com  2005-12-20 07:40 -------
Subject: Re:  REGREGRESSION: SSE2 vectorized code is many
 times slower on 4.x.x than on 3.4.4

Now this huge runtime difference disappeared
but now 4.0.2-generated code is always ~> 20% slower.
Many memory accesses where they are not needed at all and did not exist 
for 3.4.4.

I tried -march=i686 and -march=k8, both are slower than 3.4.4.

Do I also have to recompile gcc with some special options?

Yuri


pinskia at gcc dot gnu dot org wrote:

>------- Comment #10 from pinskia at gcc dot gnu dot org  2005-12-20 06:55 -------
>Oh, I looked a little more and yes it depends on the arch you are building for
>but only for 4.x.
>
>Since you are using SSE, you should add also -march=i686 or -march=k8 so that
>the code is also tuned for the processor you are using.  
>
>Anyways the problem with i386 with 4.0 is really just PR 14295.
>
>
>  
>


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25500