Messages in this thread | | | Date | Tue, 29 Jul 1997 16:47:31 +0200 (MET DST) | From | Ingo Molnar <> | Subject | Re: Interesting pentium-memcpy results |
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On Tue, 29 Jul 1997, Robert L Krawitz wrote:
> the 'soft' routine is not complete, eg. it does not save FPU flags .. but > it saves the 'main bulk', the 80 bit FPU registers. Maybe there are other > things too to save? Everything that might be affected by those fildl and > fistl instructions should be saved. > > There's also the issue of making certain that the FPU is in a sane > state. If the FPU's in a weird state, it's possible that fildq/fistpq > might not do the right thing, although I don't know that for certain.
another speedup for the soft method: to analyse 'stacktop', and do less stores/restores if it's less than 8. Usually it's 0 or 1?
FPU states are clearly defined. I think we cant even mess up NaN's with 'fldt' 'fstpt'? Not sure about the per-register 'tag' bit.
-- mingo
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