https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61515
--- Comment #26 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to Jeffrey A. Law from comment #25) > So I think there's another approach. invalidate_equivalences is passed in > the stack of temporary equivalences, which include those created by jump > threading as well as those created by DOM. > > This means that in theory, we could walk that stack (in reverse order) to > find all the equivalences we need to invalidate. If the stack has fewer > entries than we have SSA_NAMES, then we win. > > For the stripped down testcase in this PR we go from ~40 seconds to ~1 > second in the relevant part of the compiler with a hack that does exactly > what's described above. > > I need to do a bit more review/research, but it looks like a promising > alternative. Huh, I thought I suggested that somewhere but you said the information is not available here. But yes, this sounds exactly what we want to do complexity-wise. I suppose we would need to amend the stack of tempoary equivalences to record the basic-block we are creating the actual set of equivalences for (to be able to terminate the walk?)
