HardFP

GoogleGroups
1

Hi,

I have a couple questions about hardware float point support on Beagleboard:

  1) Does this board have VFP and Neon support?
  2) How to get a gcc to generate hardfp instrutions (i don't want to
use softfp)?

Thanks in advance,
Eduardo

2

  1) Does this board have VFP and Neon support?

yes. neon and vfpv3.

  2) How to get a gcc to generate hardfp instrutions (i don't want to
use softfp)?

gcc 4.5 can generate hardfp.

it would be much easier to wait for an arm hardfp distro.

i think you can run hardfp on soft distros but you have to
have your own version of every library with functions with
floating point arguments compiled that way too. static linking
is probably the safest way. all the libraries that you need
may not have been ported to hardfp yet.

softfp (vs soft) can run fairly fast because it'll generate
vfp instructions inline. so basic arithmetic goes fast.

what's your application? is that good enough?

3

Like this: http://dominion.thruhere.net/koen/angstrom/beagleboard/hardfloat/ ?

4

Hello Andrew,

Thanks for your reply.

gcc 4.5 can generate hardfp.

Do you know how to compile gcc 4.5 for arm? I am using crosstools-ng,
but it does not have a gcc 4.5 option.

static linking
is probably the safest way. all the libraries that you need
may not have been ported to hardfp yet.

I am considering static linking so that I don't need a complete hardfp distro

softfp (vs soft) can run fairly fast because it'll generate
vfp instructions inline. so basic arithmetic goes fast.
what's your application? is that good enough?

My application is a numeric intensive fortran application. I tried the
default compiling options of the gfortran I found on Angstrom. The
performance was pretty low. I want to use hardfp to see if it improves
performance.

Best regards,
Eduardo

5

Hi Koen, Is this a hardfp Angstron distro? Does it have a gcc that
generates hardfp code?

Regards,
Eduardo

6

I use openembedded and am quite happy with it. It might be a bit
overkill for just getting a cross-compiler, but it's quite nice to work
with.

- Ben

7

is the default soft or softfp?

did you try Koen's rootfs?

8

That's a hardfp images, yes and no, it doesn't include gcc.

To rebuild that follow the instructions on the angstrom website and add ARM_FP_MODE = "hardfp" to your local.conf

regards,

Koen

9

Andrew,

is the default soft or softfp?

I don't know. My board is not handy now and the gcc documentations
only says "the default depends on the specific target configuration".

Does anyone in this list know what is the default floating-point ABI
of gcc on Beagleboard?

did you try Koen's rootfs?

I will give a try.

Eduardo

10

For the record, the application profile in the Cortex A8 requires the
implementation of VFP co-processor support. I doubt we'll see boards
without hardFP support based on these modern cores.

Jon.