Mailinglist Archive: opensuse-arm (41 mails)

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Re: [opensuse-arm] bootstrapping current Factory for ARM
On Mon, September 26, 2011 1:07 pm, Alexander Graf wrote:
On 09/26/2011 10:26 AM, Guillaume Gardet wrote:

Le 25/09/2011 10:40, Andrew Wafaa a écrit :
On 23 September 2011 19:12, Dirk Müller<dmueller@xxxxxxx> wrote:

[...]
We've also setup openSUSE:Factory:ARM, which is supposed to
bootstrap itself
and become a complete Factory distribution. We'll be working on this
during
the next week. Currently this project is empty and not yet building
due to
some initial issues still.

Currently we're building armv7el with softfp, although people have been
indicating that we should switch to hardfp, and revive armv5el for
the softfp
targets. Any other comments?
My thinking behind preferring hardfp is that the boards/systems that
we will hopefully be running on (at least initially) will be the newer
variaty which support hardfp. My understanding of the situation is
that there is a significant gain if using hardfp vs softfp. Saying
that though I am open to being educated on the situation. I know our
competitors/peers are all switching to hardfp too.

According to GCC man page:
http://gcc.gnu.org/onlinedocs/gcc/ARM-Options.html
softfp option uses hardware instructions.
Quote:
****************************
-mfloat-abi=name
Specifies which floating-point ABI to use. Permissible values are:
`soft', `softfp' and `hard'.

Specifying `soft' causes GCC to generate output containing library
calls for floating-point operations. `softfp' allows the generation of
code using hardware floating-point instructions, but still uses the
soft-float calling conventions. `hard' allows generation of
floating-point instructions and uses FPU-specific calling conventions.

The default depends on the specific target configuration. Note
that the hard-float and soft-float ABIs are not link-compatible; you
must compile your entire program with the same ABI, and link with a
compatible set of libraries.
****************************

So be sure everyone is speaking about the same thing.

While VFP is still optional in the architecture, I'd say every system we
really want to run openSUSE on should have VFP available. If not, I'd
much rather go the PowerPC road and implement an FPU emulator in the
kernel rather than confine all user space to a slow ABI. Soon targets
without FPU will be gone - and we're not targeting the past here.

Would this be comparable to the "wm-FPU-emu is an FPU emulator for Linux"?
http://kernelhistory.sourcentral.org/linux-0.99.9/S/294.html

I think that would be a great option as the primary support will be new
hardware while old hardware is still supported.

So yes, we should go with hardfp.


Alex


Joop.



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