[Bug middle-end/123115] -Wunused-but-set-variable warning for EH_RETURN_DATA_REGNO on nvptx

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123115

--- Comment #2 from Sam James <sjames at gcc dot gnu.org> ---
(In reply to Sam James from comment #1)
> See r6-156-g9a52250502b8e0 and r15-9470-gfe283dba774be5.

That is, it is not clear to me if this code is actually OK or not (is
EH_RETURN_DATA_REGNO's result ever used on nvptx? if so, a check is needed for
whether it is INVALID_REGNUM). r15-9470-gfe283dba774be5 implies it is
sometimes.