[Bug ipa/98925] Extend ipa-prop to handle return functions for slot optimization

[hubicka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98925

--- Comment #3 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
Return value range propagation was added in
r:53ba8d669550d3a1f809048428b97ca607f95cf5

however it works on scalar return values only for now. Extending it to
aggregates is a logical next step and should not be terribly hard.

The code also misses logic for IPA streaming so it works only in ealry and late
opts.