[PATCH] Add fast little-endian switch system call

[Paul Mackerras]

Christoph Hellwig writes:

> Am I missing something here or does this add a branch for every normal
> syscall?

It does, but the impact is so small as to be unmeasurable with
lmbench, even on the null syscall measurement.  The overhead of the
easily-predicted not-taken branch is completely swamped by the amount
of time that the sc and rfid instructions take.  I had it under a
config option at one point but then decided not to bother with that
when I couldn't measure any difference.

Paul.