[Bug c/58884] OPTIONAL warning when a temprary value is created and not used.

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58884

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
> (In reply to Max TenEyck Woodbury from comment #1)
> > I found the relevant code in the "gimplify" modules. 
> 
> This is the wrong location for this kind of warning.
> 
> The correct location is where the -Wunused-value warnings are emitted.

warn_if_unused_value is the best place to warn.