On Wed, 7 Feb 2001, Florian Lohoff wrote:
> The problem with not compiling in the FPU Emulator at all means some
> of your FPU instructions (even on FPU hardware) will fail as on some
> specific operators the hardware decides to handle it in software. So
> usually you would need an FPU Emulator even on FPU enabled CPUs.
I mean a full emulator. I know that for simplicity certain actions
required by the IEEE spec are handled in software (Alpha does it as well).
These bits have to be always included, of course. I would like to save
wasted bits for hardware that always has an FPU, though.
> This isnt true if you decide to compile your complete userland with
> fpu emulation.
I'm not sure if that approach has any advantages when using an operating
system such as Linux. It might certainly be beneficial for firmware or
similar dedicated software.
> I dont know if this is a generic way to go - I saw complete "full-stops"
> on an R3912 using the ctc/cfc instructions - I'll try the autodection
> when i come home.
We might work around pathological cases as usual -- such a behaviour
should count as a bug (I hope IDT did have a clue here -- is there any
original MIPS statement on how to handle FPU presence detection?). You
might use the i386 setup code for a reference as a large mine of bug
workarounds.
Maciej
--
+ Maciej W. Rozycki, Technical University of Gdansk, Poland +
+--------------------------------------------------------------+
+ e-mail: macro@ds2.pg.gda.pl, PGP key available +
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