Re: How to build ARM hardfp/NEON toolchain with crosstool-ng

[Tomasz Ostaszewski <tomasz dot ostaszewski at interia dot pl>]

Not altogether sure, as we don't have my crosstool env right now, but
doesn't the '<crosstool dir>/share/doc/' directory contain an
appropriate example ".config" file? I do recall building such a NEON
capable toolkit for Beaglebone/Cortex-A8. The '.config' used was a
minor tweak to the example '.config'.

t.

On Tue, Jul 31, 2012 at 4:20 PM, Peter Barada <peter.barada@logicpd.com> wrote:
> On 07/30/2012 05:30 PM, Michael Hope wrote:
>> On 31 July 2012 02:40, Peter Barada <peter.barada@logicpd.com> wrote:
>>> I'm trying to target a Cortex-a8, and want to build a single toolchain
>>> that can be used to build both hardfp as well as NEON executables (I
>>> don't believe I'll ever want to mix those two variants within the same
>>> program).
>>>
>>> If I understand correctly, hard float for VFP3 requires
>>> "-mfloat-abi=hard -mfpu=vfpv3" and NEON requires "-mfloat-abi=softfp
>>> -mfpu=neon".
>> Hi Peter.  The ABI sets how floating point values are passed between
>> functions, while the FPU tells GCC the capabilities of your hardware
>> and what instructions it can use.  NEON is a superset of VFPv3 so you
>> can use the hard float ABI always, default to VFPv3, and then enable
>> NEON for any programs that benefit from it.
>>
>> Our pre-built toolchain is pretty close to what you describe:
>>  https://launchpad.net/linaro-toolchain-binaries
>>
>> It's crosstool-NG based, tuned for the Cortex-A9, uses the latest
>> Linaro releases, and the source is there if you want to tweak it.
>> See:
>>  https://launchpad.net/linaro-toolchain-binaries/trunk/2012.07/+download/README.txt
>>
>> for more.
> Thanks for the pointer, I'll have to give it a whirl.
>
> What flags would you pass to get full NEON, "-O3 -ftree-vectorize
> -mfpu=neon -ffast-math -funsafe-math-optimizations
> -fsingle-precision-constant"?
>
> Thanks in advance!
>
> --
> Peter Barada
> peter.barada@logicpd.com
>
>
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