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

Kumar Gala galak at kernel.crashing.org
Thu Nov 22 01:19:19 EST 2007

On Nov 21, 2007, at 3:12 AM, Benjamin Herrenschmidt wrote:

> 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.

I think having some form of per insn group counters would be useful as  
well.  I know it would be helpful to debug user problems if they are  
doing a lot of FP emu or the like and don't know it.

- k

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