[Bug target/78386] [PPC] Optimization -O2 and higher cause math inconsistency

[dje at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78386

--- Comment #10 from David Edelsohn <dje at gcc dot gnu.org> ---
-std=gnuXX affects IEEE 754 conformance, but that is not mentioned in the
documentation, only in source code comments (c-family/c-cppbuiltin.c)