[v2,1/1] fftw: add compile precision option

From: Gwenhael Goavec-Merou <gwenhael.goavec-merou@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.

Signed-off-by: Gwenhael Goavec-Merou <gwenhael.goavec-merou@trabucayre.com>
---
Changes v1 -> v2:
 * FFTW_CONFIGURE_OPTS -> FFTW_CONF_OPTS
---
 package/fftw/Config.in | 32 ++++++++++++++++++++++++++++++++
 package/fftw/fftw.mk   | 10 ++++++++++
 2 files changed, 42 insertions(+)

Dear Gwenhael Goavec-Merou,

On Fri, 13 Mar 2015 11:25:02 +0100, Gwenhael Goavec-Merou wrote:
> From: Gwenhael Goavec-Merou <gwenhael.goavec-merou@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:

BR2_arm=y
BR2_TOOLCHAIN_EXTERNAL=y
BR2_TOOLCHAIN_EXTERNAL_CUSTOM=y
BR2_TOOLCHAIN_EXTERNAL_DOWNLOAD=y
BR2_TOOLCHAIN_EXTERNAL_URL="http://autobuild.buildroot.org/toolchains/tarballs/br-arm-full-2014.11.tar.bz2"
BR2_TOOLCHAIN_EXTERNAL_HEADERS_3_17=y
BR2_TOOLCHAIN_EXTERNAL_LARGEFILE=y
BR2_TOOLCHAIN_EXTERNAL_INET_IPV6=y
BR2_TOOLCHAIN_EXTERNAL_LOCALE=y
# BR2_TOOLCHAIN_EXTERNAL_HAS_THREADS_DEBUG is not set
BR2_TOOLCHAIN_EXTERNAL_INET_RPC=y
BR2_TOOLCHAIN_EXTERNAL_CXX=y
BR2_INIT_NONE=y
BR2_SYSTEM_BIN_SH_NONE=y
# BR2_PACKAGE_BUSYBOX is not set
BR2_PACKAGE_FFTW=y
BR2_PACKAGE_FFTW_PRECISION_SINGLE=y
# BR2_TARGET_ROOTFS_TAR is not set

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.

Note: if your only need is "single precision" mode, then I wouldn't
mind receiving a patch that allows enabling only this mode. People
interested in long double and quad precision can enable such options
later.

Best regards,

Thomas Petazzoni

Dear Thomas Petazzoni

On Fri, 13 Mar 2015 23:25:21 +0100
Thomas Petazzoni <thomas.petazzoni@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@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.

[SNIP]
> 
> 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.
[SNIP]

Regards 
Gwen