Re: Re: arm softfp compatibility arch/fpu in gcc-4.8.2

[John Spencer <maillist-musl@barfooze.de>]

David Wuertele wrote:
> John Spencer <maillist-musl <at> barfooze.de> writes:
> 
>>> arm-linux-musleabihf/4.8.2/../../../../arm-linux-musleabihf/bin/ld: failed to
>>> merge target specific data of file lib/armeabi/libXXX.a(YYY.o)
>>>
>>> What arch/fpu should I use to build a toolchain that can link against this
>>> library?
>> if you need to link to proprietary softfloat modules, you have to use 
>> "softfp" float mode. that one is compatible to soft, but makes full use 
>> of the FPU.
> 
> Thanks!  That was what I was hoping.
> 
> I see that gcc-4.8.2 supports "--with-float=softfp".  I'm confused about what
> to use for "--with-fpu", if anything.  My choices are:
> 
> 		| vfp | vfp3 | vfpv3 \
> 		| vfpv3-fp16 | vfpv3-d16 | vfpv3-d16-fp16 | vfpv3xd \
> 		| vfpv3xd-fp16 | neon | neon-fp16 | vfpv4 | vfpv4-d16 \
> 		| fpv4-sp-d16 | neon-vfpv4 | fp-arm-v8 | neon-fp-armv8 \
>                 | crypto-neon-fp-armv8)
> 
> If I omit the "--with-fpu", will it just default to use soft float all the time?

not sure what the default is, but afaik vfp is the most compatible one 
(only needed when you want to create binaries that work on way less 
decent arm chips).
if you want the best speed, pick one of the neons - not sure which one 
your chip supports though. cortex A8 already supports neon, so that one 
should definitely work for you while giving decent performance.
in doubt, ask your vendor for the best setting.