[Buildroot] Question about float-abi

[Ludovic Desroches]

Hello Thomas,

On 02/29/2012 03:47 PM, Thomas Petazzoni wrote:
> Hello Ludovic,
>
> Le Wed, 29 Feb 2012 14:49:09 +0100,
> Ludovic Desroches <ludovic.desroches at atmel.com> a écrit :
>
>> Yes there were missing options for gcc: --with-float=hard and
>> --with-fpu=...
>>
>> Now floating score is correct. I am surprised by the good results of
>> the uclibc. I don't know if nbench is an accurate benchmark to test
>> several libc but scores obtained by glibc, eglibc and uclibc are very
>> closed.
> As I told you on IRC, those investigations are really interesting. We
> know that the Buildroot support for floating-point is far from perfect,
> this has been briefly discussed during the last Buildroot Developer
> meeting. If you want to improve this part of Buildroot, do not hesitate
> to send patches, we are definitely interested.
>
> I guess with internal toolchains, it's quite easy to improve things.
> The case of external toolchains is probably a bit more complicated,
> since we do not control how the C library of the external toolchain has
> been built in terms of floating point support.
>
I agree using external toolchain even those generated by crosstool-ng
can be a little more complicated. I was mostly worried about reproducibility
since I had some troubles to generate my toolchain with crosstool-ng:
the version of some packages were not compatible, I need specific package
version on host side, etc.
Crosstool-ng is a great tool to tune your toolchain and show me missing
options into Buildroot to support hard floating point.

Buildroot allows me to do what I want so it's good for me. The only thing
I can 'criticize' is that some options like BR2_VFP_FLOAT seem to enable
the hardware floating point support but in fact no, we need to set extra
settings.

I will try to give you extra feedbacks and to send some patches.


Regards

Ludovic