[OE-core] Enabling NEON instructions for fftw

[Mark Hatle]

On 1/3/13 12:42 PM, Philip Balister wrote:
> So, recent versions of fftw have NEON support for the single precision
> build. In the poast, I just passed --enable-neon to configure or the
> armv7a case. Now, this is not entirely correct, since some armv7a's lack
> a NEON coprocessor.
>
> Does anyone have a suggestion for how to handle this better? Personally,
> I think if you want to run fftwf without NEON, you should have your head
> examined, but I would like to avoid generating packages that SIGILL on
> people.

This says to me that either you need a machine specific package, or use an 
alternative architecture for that package.. (that is compatible).. then the 
package can switch neon on/off depending on arch of tuning flags.

There is an armv7a-neon tuning defined.  This enabled the TUNE_FEATURES of 
'neon'.  So you should be able to check for that in the fftw recipe, and enable 
the --enable-neon when it's set.  (Using PACKAGECONFIG is likely best...)

Then you can change the DEFAULTTUNE_<recipe> = "armv7-neon" in your local.conf.

--Mark

> Philip
>
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