[Bug target/80834] PowerPC gcc -mcpu=power9 seems to turn off vectorization that -mcpu=power8 enables

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80834

--- Comment #3 from Michael Meissner <meissner at gcc dot gnu.org> ---
It looks like -fvect-cost-model=unlimited seems to re-enable vectorization with
-mcpu=power9.  It also enables some vectorizaton with -mcpu=power7.