Re: [ANNOUNCE] ktimers subsystem

[George Anzinger]

Tim Bird wrote:
> Roman Zippel wrote:
>
> > On Sun, 25 Sep 2005, Thomas Gleixner wrote:
> >
> > > Can you please point out which architectures do not have a 32x32->64
> > > instruction ?
>
>
> <snip>
>
> > For the rest you might want to check <asm/div64.h>, if div64 has to be 
> > emulated, there are good chances this instruction has to be emulated as 
> > well (especially in smaller embedded archs).
>
>
> Hmmm.  In my experience, there are several embedded platforms
> with a 32x32->64 instruction, which are lacking a div64 instruction.
> I don't think checking for div64 is a very good metric here.

Also, even having a div64 instruction does not eliminate the asm/div64.h 
as it checks for results that are >32-bits and does the right thing. 
For example, letting the x86 do this divide with such a result, results 
in a trap.

This is why we need to be very careful where we use the div_ll_l_rem() 
which accesses just this instruction.

--
George Anzinger   george@xxxxxxxxxx
HRT (High-res-timers):  http://sourceforge.net/projects/high-res-timers/
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