[Bug target/78602] PowerPC vec-extract-v2df.c can fail if -mcpu=power9 -O0

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78602

--- Comment #1 from Michael Meissner <meissner at gcc dot gnu.org> ---
Created attachment 40195
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40195&action=edit
Proposed patch to fix the problem