Changing CFLAGS for i386 packages on x86_64

dragoran dragoran at feuerpokemon.de
Fri Jul 14 08:47:27 UTC 2006


Arjan van de Ven wrote:
> On Fri, 2006-07-14 at 10:06 +0200, dragoran wrote:
>   
>> Paul Howarth wrote:
>>     
>>> On Fri, 2006-07-14 at 08:13 +0200, dragoran wrote:
>>>   
>>>       
>>>> On i386 most of the packages are i386 and there are some i686 one like 
>>>> kernel and glibc.
>>>> On x86_64 there are some i386 packages installed by default too. Why are 
>>>> they compiled with the same settings as on i386?
>>>> On x86_64 it wont hurt enabling i686 (cmov) and see2 because all x86_64 
>>>> cpus support this instructions.
>>>>     
>>>>         
>>> Doing this would result in i386 packages in the x86_64 repo that are
>>> different from the identically-named i386 packages in the i386 repo,
>>> wouldn't it, since all Fedora arches are built from exactly the same
>>> SRPMS?
>>>
>>> Paul.
>>>
>>>
>>>   
>>>       
>> no it wont because they will be i686 builds and RPM_OPT_FLAGS would be 
>> differnet so the same SRPM can be used.
>>     
>
>
> but to what point?
>
> I will actually here propose to stop doing i686 builds for most of the
> things it's done now; cmov just isn't worth it, and if you want to use
> SSE in 32 bit, that's not going to be cheap either (unlike 64 bit where
> it's a standard part of the ABI); SSE in 32 bit is not "just used" by
> gcc, only hand coded assembly uses it basically, and those can use .i386
> just fine since generally they have a runtime detection mechanism.
>
>   
what do you mean by not used by gcc? there are flags to use it -msse2 ...
many apps have runtime detection and use handcoded assembly but not all 
of them
> And for optimization... even the i386 rpms are already optimized for
> modern processors so there's no difference there either.
>
>   




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