floating point support for ARM
dchkeller at gmx.ch
Thu Jun 16 21:35:01 CEST 2005
Thanks for your answer.
> You can use either kernel-fpe (two choices: NWFPE or FastFPE), or
> soft-float is integrated into recent gcc+binutils. The latter is
> highly recommended for performance, since the kernel-mode method
> incurs exectption and context switch overhead.
We have compiled the hole environment with a soft-float-compiler, but
the FPE is still on in kernel-config.
>> Actually we've tried the example from
>> http://www.captain.at/programming/rtai/examples.php, but when loading
>> the module we get some unresolved symbols (looks like floating-point
>> support is missing). The same if we try to load rtai_math. We're
>> using a softfloat-compiler (gcc 3.3.3).
> Normally floating-point is not allowed in the kernel.
But shouldn't RTAI allow to do this in real-time tasks?
> With soft-float it might be possible (I have never tried) as long as
> you take care to link statically all the libraries with the FP
> functions into your module.
Since the hole environment is compiled with soft-float, we didn't link
it satically. We thought statically linked libraries are only necessary,
if only a part of the system uses soft-float and another one uses the
kernels FPE. Please correct me, if this I'm wrong here.
> The traditional way is to do messy FP stuff in userspace.
But LXRT is missing for ARM, so real-time FP stuff should be done in
kernel-space, shouldn't it?
Thanks and best regards
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