Re: [Qemu-devel] [PATCH] MIPS instruction set configuration

[Thiemo Seufer <ths@networkno.de>]

Fabrice Bellard wrote:
[snip]
> >>>There is no good reason to make 
> >>>the selection at compile time because the translator can efficiently 
> >>>handle any CPU differences at runtime.
> >
> >
> >I'm a bit dubious about this argument, each instruction needs to be
> >checked agains a tuple of values. How much performance loss would be
> >acceptable?
> 
> It slows down the translator a bit, but most of the time is spent in the 
> generated code, not in the translator (otherwise there is no point in 
> doing dynamic translation !).

Well, based on that theory I moved the CP0 register handling to dynamic
translation. The patch was rejected because I had no effective method
to assess the performance gain. So I wonder what the accepted tradeoffs
for the implementation are.


Thiemo