https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89150
--- Comment #3 from Nathan Sidwell <nathan at gcc dot gnu.org> ---
I didn't know there were no tree-form bitmaps yet.
Contrary to my original assertion, I think just dropping the chain_prev
("%h.prev") marker will suffice. Normal use of a list-form bitmap starts at
the head. The only way to keep hold of an internal pointer is by looking
behind the API.
For tree-form bitmaps we'd iterate down the right-hand branch and recurse on
the left hand ones.
