https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62291
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> --- So what remains is insertion computing whether a value is available on some predecessor (partial redundancy) or all (full redundancy) which needs AVAIL_OUT for the predecessors and the immediate dominator. Then the actual insertion code needs to lookup leaders for expression operands it wants to insert. I think this part can be easily delayed until eliminate if we store all necessary information in some new data structure. The first part is harder - especially as it is that what needs to be iterated (with taking into account newly inserted stuff). One could imagine iterating over sucessors of a block (and immediate dominated-bys) and compute "candidate" sets, both pruning and extending it during the iteration.
