[OT?] Unimplemented instructions on a G5?

Pantelis Antoniou panto at intracom.gr
Thu Apr 1 23:51:12 EST 2004


I've recently came across a very strange problem.

I have some PPC code with some inline assembly for implementing
saturated arithmetic.

The code runs fine on a 8xx target and on the G4 development host.

When I upgraded to a G5 running Gentoo the same code terminates
with an illegal instruction trap.

The offending instruction is the seemingly harmless:

  mcrxr crX

   (Move to condition register from XER).

Does anyone have any idea if IBM left this instruction
unimplemented. Searching the docs I've found nothing.

It's not a deal-breaker but it is inconvinient to not be
able to run the target binaries on the host.

If it is unimplemented any idea of how hard it will be to
trap and emulate it?



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