[PATCH] [POWERPC] Emulate isel (Integer Select) instruction

[Geert Uytterhoeven]

On Wed, 21 Nov 2007, Kumar Gala wrote:
> On Nov 21, 2007, at 7:09 AM, Geert Uytterhoeven wrote:
> > On Tue, 20 Nov 2007, Kumar Gala wrote:
> > > On Nov 20, 2007, at 11:54 AM, Scott Wood wrote:
> > > > On Mon, Nov 19, 2007 at 09:36:57PM -0600, Kumar Gala wrote:
> > > > > isel (Integer Select) is a new user space instruction in the
> > > > > PowerISA 2.04 spec.  Not all processors implement it so lets emulate
> > > > > to ensure code built with isel will run everywhere.
> > > > 
> > > > Given that the instruction is meant to be a performance enhancement,
> > > > we should probably warn the first few times it's emulated, so the user
> > > > knows they should change their toolchain setup if possible.
> > > 
> > > The same is true of mcrxr, popcntb, and possibly string ld/st.
> > > 
> > > Feel free to submit a patch that warns about their usage.
> > 
> > Something like this?
> > 
> > Probably we also want it for:
> > 
> >  - arch/powerpc/kernel/align.c
> >      o emulate_dcbz()
> >      o emulate_multiple()
> >      o emulate_fp_pair()
> >      o emulate_spe()
> > 
> >  - arch/powerpc/kernel/softemu8xx.c
> >      o Soft_emulate_8xx()
> > 
> >  - arch/powerpc/kernel/traps.c
> >      o SoftwareEmulation()
> 
> You missed math_emu.
> 
> >   - arch/powerpc/kernel/vecemu.c
> >      o emulate_altivec()
> 
> I'm not sure I would concern this one emulation, there isn't much you can do
> about the denorm fixup.
> 
> How about some per processor counters in sysfs under the processor.

Good idea!

> > Question: do we want it for emulate_single_step(), too?
> 
> What do you mean, we should could the emulation, the emulate single step just
> is for handling if you are doing debug while hitting an emulated insn.

I mean: should these be counted?

With kind regards,
 
Geert Uytterhoeven
Software Architect

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