On Thu, 21 Feb 2013, Jan Hubicka wrote: > > > > Hunting for the "we're getting slower" bits I noticed that > > > TODO_remove_unused_locals is a big part of execute_function_todo > > > (and accounts for 1% of compile-time of ac.f90). > > > The following patch removes most of the remove_unused_locals > > > calls based on the fact that with anonymous SSA names now available > > > we should never create new locals (wishful thinking of course ...) > > We still can kill references to existing ones. > > > > and the important places to remove unused stuff are driven by > > > 1) avoid creating yet another copy of the unused stuff, thus do > > > it before inlining, on the callee; 2) avoid pinning unused memory > > > while we operate on other function bodies, thus, do it at the end > > > of non-IPA pass pipelines > > > > > > In the end this asks for more explicit placement and thus a > > > real pass ... but the following should be enough as a RFC and > > > be good enough for 4.8. > > Yes, it looks good to me. I introduced this remove_unused_locals stuff > and I was aware it is executed quite too often. I meant to get some data on > this > but never got around that and moreover the number of execution has increased > over the years as we increased number of passes... > > My recollection is that at that time the pass also did dropping of some flags > (ADDRESSABLE?) promoting into Gimple registers. This was motivation to keep > it working often since it was code quality thing too. I suppose this is now > done elsewhere.
Yes, that's done with TODO_update_address_taken which is done in a more controlled fashion. Richard.
