This results in failures assembling "mfcr r,mask" and also wrong "at" branch hints. See https://sourceware.org/bugzilla/show_bug.cgi?id=19359 for a testcase.
As I mentioned in the binutils bug, I think -mcpu=powerpc64le should mimic -mcpu=power8. I'll have a look at making that change.
(In reply to Peter Bergner from comment #2)
> Patch summitted:
Patch committed, but without the aix*.h file hunks.
Fix backported to gcc-5-branch and gcc-4_0-branch too.
Closing as fixed.