[fedora-arm] Mandriva and Unity Linux work on armv7 port

[Paulo César Pereira de Andrade]

Em 30 de julho de 2011 02:48, Jon Masters <jcm at redhat.com> escreveu:
> On Sat, 2011-07-30 at 00:37 -0300, Paulo César Pereira de Andrade wrote:
>
>>   I did not do any performance measures so far, so
>> forgive me if the extra "vmov d#, r#,r#" or "vmov r#,r#, d#"
>> is too costly, but I think it should be worth the
>> compatibility with rpms for armv5 or earlier. It should
>> have been already discussed at fedora, but I really
>> do not know the real reason :-)
>
>>   But have already rebuilt some of the "bootstrap" mandriva
>> packages, rpm5, etc, as well as have packages built for
>> armv5 installed. This way, rebuilding for armv7 is an
>> "optimization", and have something to start with...
>
> If you're arguing that one could build support for soft float and have
> hard float as an option, I must point out that the reason we're doing
> things as we are is that the hard floating point requirement forms part
> of an ABI switch that we are making concurrent with the bringup. The

  I am saying that I find the softfp option more appealing *if* not also
switching to thumb instruction set. From gcc.info: "`softfp' allows
the generation of code using hardware floating-point  instructions,
but still uses the soft-float calling conventions". This allows armv5
packages, to work because they use the same calling convention,
and the abi difference is only that it now pass/return values in
vfp registers, and, to conform to abi, should use only two registers
anyway.

> newer ABI is intentionally incompatible, but can be thought of as an
> architecture revision since we're requiring v7+ at the same time.
>
> We don't have years of ARM backward compatibility to worry about, so now
> is the time to move to the newer ABI, which everyone else is moving to
> at the same time. Once we're super successful and famous, and a primary
> architecture with millions of users, then we can worry about any changes
> we might make in the future. At this stage Fedora ARM doesn't have the
> history to justify putting off making a switch, and we'll keep a v5
> build of the packages around for those who want that longer term.
>
> Jon.

Paulo