Re: [hatari-devel] Getting cycles used by previous or next instruction without modifying CPU state?

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

On 22/02/2012 20:39, Eero Tamminen wrote:
> Hi,
>
> On tiistai 21 helmikuu 2012, Nicolas Pomarède wrote:
> > On 20/02/2012 23:50, Eero Tamminen wrote:
> > > How do I get how many cycles previous instruction used, for
> > > profiling purposes?
> > >
> > > src/debug/profile.c has this code:
> > >           Uint32 opcode, cycles;
> > >           opcode = get_iword_prefetch (0);
> > >           cycles = (*cpufunctbl[opcode])(opcode) + nWaitStateCycles;
> > >
> > > But that's bad, calling the opcode table function modifies
> > > the CPU state.
> >
> > I don't think you can get this easily. Only the current instruction
> > cycles are available.
>
>  From where?

Well, it's almost everywhere in the traces I added in various parts :) 
-> CurrentInstrCycles

> > If that's just for test purpose, you can add some kind of breakpoint
> > that would trigger on every instruction and then save the current cycles
> > in your own variable. But this would certainly slow down emulation a lot.
>
> This is for the profiler.  If it cannot get the cycles either for previous
> or next instruction without modifying/invalidating CPU state, it's better
> if I remove that part.

Then I guess it won't be possible. Calling opcode() will really run the 
instruction (and change cpu/memory), and some instructions have variable 
number of cycles depending on their parameters (lsl, rol, mul, div, ...)


Nicolas