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

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Tue, 2007-11-20 at 15:01 -0600, Kumar Gala wrote:
> > 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.

At least we should keep counters... best would be per-task counters
in /proc but that sounds harder :-)

I remember in the early days of powerpc, it wasn't uncommon to have apps
with issues because they used 601 only bits on 603/4 that had to be
emulated (such as old POWER opcodes). On MacOS, we used to have a
system-wide counter of the number of emulated instructions we could use
to detect these things.

Ben.