[Buildroot] [PATCH v2 1/1] fftw: add compile precision option

gwenhael.goavec gwenj at trabucayre.com
Sat Mar 14 07:39:56 UTC 2015

Dear Thomas Petazzoni

On Fri, 13 Mar 2015 23:25:21 +0100
Thomas Petazzoni <thomas.petazzoni at free-electrons.com> wrote:

> Dear Gwenhael Goavec-Merou,
> On Fri, 13 Mar 2015 11:25:02 +0100, Gwenhael Goavec-Merou wrote:
> > From: Gwenhael Goavec-Merou <gwenhael.goavec-merou at trabucayre.com>
> > 
> > fftw has options to select compile precision between single, long-double and
> > quad. These options are exclusives. This patch adds choice to select precision
> > option.
> Unfortunately, the quad precision support doesn't build, because not
> all toolchains have libquadmath in gcc:
> checking for sinq in -lquadmath... no
> configure: error: quad precision requires libquadmath for quad-precision trigonometric routines
> And the long double precision support also doesn't build:
> checking for cosl... (cached) no
> configure: error: long-double precision requires long-double trigonometric routines
> This was generated by the following defconfig:
It's true. libquadmath is only enabled on x86 and x86_64. I must add a depend
on BR2_i386 || BR2_x86_64.

> Also, I see that FFTW has some NEON, Altivec, MMX and SSE/SSE2
> optimizations. Maybe it would make sense to enable them when the CPU
> supports them. However, beware that many of those optimizations only
> work in "single precision" mode.
Yes. I plan to add these optimizations but that's for a future patch.


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