[Bug target/116063] [PPC] Transparent union issue with signedness when optimizing

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116063

--- Comment #4 from Segher Boessenkool <segher at gcc dot gnu.org> ---
The two members have the same in-memory representation, but transparent_union
is explicitly only about function arguments, so Andrew's arguments are very
valid I think.

It would be nice if we could warn about this, but it might not be possible
at all, or not easily doable.  There is certainly no requirement for a
diagnostic here.