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

[Michael Hope <michael dot hope at linaro dot org>]

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.

-- Michael

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