[Bug middle-end/38474] compile time explosion in dataflow_set_preserve_mem_locs at -O3

[hubicka at ucw dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38474

--- Comment #82 from Jan Hubicka <hubicka at ucw dot cz> ---
> > Yep, this is because they used to be arrays indexed by symbol UIDs which
> > Martin converted to hash tables.  Inliner happily calls summary_get each
> > time it needs the summary.  I have some patches to speed this up which I
> > will push out after the type changes (while they add bit of extra
> > functionality by teaching ipa-predicates abou value range I hope they
> > are OK for early stage3).
> 
> Awww.  I guess with no longer re-using UIDs we then get bad hashing
> behavior as well :/  I hope the hash function is _not_ simply the UID?

Yep, UID reuse was there precisely to make the arrays reasonably
compact.  hash is int_hash which IMO returns simply uid.