[Bug tree-optimization/97630] [11 Regression] SLP vectorizer leaks memory

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97630

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
The least resistance attempt to fix it would be to keep track of allocated
SLP trees in _slp_tree::operator new/delete using a hash_set<> for example
and call the DTOR on still allocated ones when destroying the alloc-pool.
A double-linked list of all allocated nodes would work as well.

Otherwise each vect_free_slp_tree would need to check whether it was the
last entry into a cycle which would be quite expensive.

Tracking cycle [entries] separately is somewhat difficult since via
vectorizable_* we can later break cycles at arbitrary places so we can't
use weak references for backedges because what and what is not a backedge
can change.