[Bug target/8243] GCC 3.2 does not check for CMOV instruction before generating code

[behrisch at informatik dot hu-berlin dot de]

------- Additional Comments From behrisch at informatik dot hu-berlin dot de  2005-02-16 09:41 -------
(In reply to comment #4) 
> From: Pete Gontier <kokorozashi@gontier.org> 
> To: <gcc-gnats@gcc.gnu.org>, 
>         <forsmark@odense.kollegienet.dk <gcc-bugs@gcc.gnu.org   
<nobody@gcc.gnu.org     <gcc-prs@gcc.gnu.orgCc:   
> Subject: Re: target/8243: GCC 3.2 does not check for CMOV instruction 
>         before generating code 
> Date: Thu, 13 Feb 2003 12:34:28 -0800 
>  
>  circa 2/13/03 11:54 AM, Pete Gontier <kokorozashi@gontier.org> wrote: 
>   
>  > I don't think I fully understand the closure of this bug. I understand if 
by 
>  > i686 you really mean Pentium Pro. (I hope that's documented.) The claim 
that 
>  > it would be dumb for GCC to generate code which checks for CMOV before 
using 
>  > it also makes sense. However, if there were a way to tell GCC not to 
generate 
>  > CMOV instructions in the first place, that would seem reasonable, too, 
>  > assuming there are other i686 optimizations worth doing. 
>   
>  Hmmm. Perhaps this is already present in the form of -march=c3. And from 
>  what I hear, CMOV was the only significant optimization for i686. 
 
This patch indicates that there -march=c3 is not the solution: 
http://gcc.gnu.org/ml/gcc-patches/2004-07/msg02718.html 
There is another (german) report on patching gcc to create optimized 
code for the c3 
http://epia.std-err.de/gcc.php 
 
Michael 

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=8243