[Bug target/27827] [4.0/4.1/4.2 Regression] gcc 4 produces worse x87 code on all platforms than gcc 3

whaley at cs dot utsa dot edu gcc-bugzilla@gcc.gnu.org
Fri Aug 4 16:24:00 GMT 2006



------- Comment #31 from whaley at cs dot utsa dot edu  2006-08-04 16:24 -------
Paolo,

Thanks for the update.  I attempted to apply this patch, but apparantly I
failed, as it made absolutely no difference.  I mean, not only did it not
change performance, but if you diff the assembly, you get only 4 lines
different (version numbers and use of ffreep rather than fstp).  Here is what I
did:
>   59  10:29   cd gcc-4.1.1/
>   60  10:30   pushd gcc/config/i386/
>   62  10:30   patch < ~/x87patch
>   64  10:31   cd ../../..
>   67  10:31   mkdir MyObj
>   68  10:31   cd MyObj/
>   71  10:32   ../configure --prefix=/home/whaley/local/gcc4.1.1p1 --enable-languages=c,fortran
>   72  10:32   make
>   73  10:58   make install

I did this on my P4e (IA32) and Athlon64 X2 (x86-64) machines.  I did have to
hand-edit the patch, due to line breaks in mouse-copying from the webpage (it
wouldn't apply until I did that), so maybe that is the problem.

Can you grab the mmbench4s.tar.gz attachment, and point its Makefile at your
modified compiler, and tell it "make assall", and see if the generated dmm_4.s
and smm_4.s are different than what you get with stock 4.1.1?  If so, post them
as attachments, and I can probably hack the benchmark to load the assembly, as
I did on the Core.

Assuming they are different, maybe you can check that this is the only patch I
need to make?  If it is, is there something wrong with the way I applied it? 
If not, maybe you should post the patch file as an attachment so we can rule
out copying error . . .

Thanks,
Clint


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27827



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