Re: NetBSD on SH-4A

On Mon, Jun 15, 2009 at 15:18:01 -0700, David S. Alessio wrote:

> I'd like to see the SH-4A fully supported.  Any suggestions on the best 
> path to get there?
>
> The approach that first comes to my mind is:
> 1)   Add kernel support for the FPU to the SH-4 arch
>    Has anyone examined this?  If so, any thoughts/suggestions on the 
> "right way" to do it?
>    I'd like to see a lazy FPU context switch.

Look at how other arches do it and do the same for SH-4 FPU.  FPU
autodetection would be nice, but compile-time kernel option could do
for now.  Shouldn't be hard, but I never got around to it as real life
keep interfering.  If you could work on it and contribute the code
back, that would be very helpful (we don't have much NetBSD/sh3
developers).


> 2)  Recompile the SH-4 world with FPU support
>    (gcc default integer division should not use the FPU)

Not sure it's possible without hacking gcc as with -m4 it generates
calls to __sdivsi3_i4 and expects its result in FPUL.

Why is this particular requirement?


SY, Uwe
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