[Bug libstdc++/78713] [missed optimization] gcc doesn't use clobbers to optimize constructors

[avi@cloudius-systems.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78713

--- Comment #4 from Avi Kivity <avi@cloudius-systems.com> ---
This bug has a cousin https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61982 where
the optimizer doesn't eliminate a store to an object that is about to be
destroyed.  While for sure it is easier to implement in the library, I think
there is a lot of potential for similar optimizations if the optimizer does get
the information it craves.