ppc64 has an extraneous variable live in some situations.
We need a better tighten pass to get rid of this extra variable.
I'm working on it, but fix the test in the meantime.

Fixes build for ppc64.

Change-Id: I1efb9ccb234a64f2a1c228abd2b3195f67fbeb41
Reviewed-on: https://go-review.googlesource.com/29353Reviewed-by: David Chase <drchase@google.com>