[Bug target/94135] PPC: subfic instead of neg used for rotate right

[jens.seifert at de dot ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94135

--- Comment #4 from Jens Seifert <jens.seifert at de dot ibm.com> ---
Setting CA in XER increases issue to issue latency by 1 on Power8.
See:
Table 10-14. Issue-to-Issue Latencies

In addition, setting the CA restricts instruction reordering.