Re: Linux 3.10-2-m68k FPU support
Thorsten,
Michael Schmitz dixit:
The docs are quite clearly out of date. From memory, there may be the
odd FPU
[…]
Seeing as this code is crucial, I'd opt for putting it back in, and
finding
These two statements are “it should be fine but I don’t really know”
and “this is important so put it back in, but I don’t remember
details”.
Andreas has been so kind as to refresh my memory on this - neither log
nor trig functions are supported.
Neither are used in the kernel, so from a kernel point of view, FPU
emulation is not a problem. From a userland point of view - if you are
looking at heavy use of these iinstructions, it might be better overall
to get a FPU (I presume all 030 models came with a FPU socket to add
the FPU later - please correct me if that is wrong for Amigas),
Together with what *is* currently in the documentation, this is
*not* reassuring, and I *know* that FPU emulation code all across
OSes (kernels and not) is a sore topic (even being kicked from
some of them).
My request for a clear statement still stands.
As per Anrdreas' comment - missing instructions. LC040 problem is well
documented and not a fault of emulation.
On the other hand, I cannot help but wonder how well it compares
to whatever ARAnyM passes as FPU. I know ARAnyM doesn’t handle the
80/64bit precision switch at all (which is why we opted to not use
I'd have to look at the code for that, but I would not bet the farm on
precision switch being supported.
that for Python), but I smell some sort of knob here… if the knob
can be used to tweak between speed and correctness, I’d opt for
correctness. (OK, BSD user speaking.) It’d probably be faster at
runtime to fix ARAnyM instead but that’s a different upstream.
If the precision switch is a feature of the 68881 or 68882, I'd argue
both are correct, and code using the FPU had better check whether
higher precision is supported.
Cheers,
Michael
bye,
//mirabilos
--
<diogenese> Beware of ritual lest you forget the meaning behind it.
<igli> yeah but it means if you really care about something, don't
ritualise it, or you will lose it. don't fetishise it, don't
obsess. or you'll forget why you love it in the first place.
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