[Bug target/63360] Does not retore f31 at -O0 across function calls

[camm at debian dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63360

--- Comment #3 from camm at debian dot org ---
Additional transcript showing the 0 f31 value is transmitted to the return of
the original call through Lnk23 in L2.