PPC float context only 4 Bytes per register?

[Sergei Organov]

Dear Thomas,

I've also noticed this some time ago and even posted my observations to this
list. However, it seems that nobody had time willingness to fix this, so I
still use old exception processing code that doesn't have this problem.

BR,
Sergei Organov.


"Thomas Doerfler" <Thomas.Doerfler at imd-systems.de> writes:
> Hi,
> 
> I have just had some looks into the 
> libcpu/powerpc/new_exception_processing/cpu_asm.S code to 
> save/restore a floating-point context. In there it seems that 
> for every context switch all the float registers are saved 
> into 4 byte locations (in "single" precision format). 
> 
> >From my point of view this results in rounding errors for 
> "double precision" (64 bit) float arithmetics. So if I have 
> written some code using "double precision" variables I will 
> get roundoff errors, if there has been a context switch during 
> calculations. (I did not try that out, but it seems logical to 
> me...)
> 
> Did I miss something there?
> 
> Any comments welcome...
> 
> 	Thomas Doerfler.
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> IMD Ingenieurbuero fuer Microcomputertechnik
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